Koskamo

sync.day MCP

A public MCP server that allows AI assistants to create group scheduling events, parse event text, read event details, submit availability, vote on times, decide on a final time, and manage participants without requiring user accounts or API keys.

Endpoint and access

No sign-in to connect and list tools. Individual tools may still need a vendor account, credentials, or permissions; check the documented prerequisites.

sync.day MCP logo, by sync.dayCommunity listingStreamable HTTPNo sign-inEndpoint checked 2026-11-06Published by sync.day
MCP endpoint (Streamable HTTP)
https://sync.day/mcp/mcp
Vendor documentation

What its tools do

8 tools, grouped by the hints the server advertises. Hints are self-declared, not verified behavior.

Read-only (2)

Can change data (6)

8 of 8 have a description · 8 of 8 declare behavior hints · 8 of 8 with parameters document them all

Checks and signals

Each line is separate evidence, not a trust score.

  • Passed Endpoint answered the live check ·
  • Availability 1 of 1 checks passed in 30 days

What you can do with it

  • Create a group scheduling event and get a share link
  • Parse natural language text into event creation inputs
  • Submit individual availability for a scheduled event
  • Decide on the final meeting time as an organizer

Source and maintenance

Community listingRegistry 1.0.0
mcp-registry: io.github.syncday-app/sync-day@1.0.0Project website

Protocol and capabilities

Server
sync.day 1.0.0
MCP protocol negotiated in check
2025-11-25
Tools
8 advertised
Resources
Not advertised
Resource templates
Not advertised
Prompts
Not advertised
Server-advertised capabilities
{
  "tools": {
    "listChanged": true
  }
}

Server-provided instructions

Untrusted server output shown for inspection. It is not Koskamo guidance and is excluded from knowledge search.

sync.day (约时间) collects availability for a fixed-length event, like When2meet. Flow: create_event (or parse_event_text first to turn a sentence into settings) -> share the returned url -> each person calls submit_availability with the start keys they can make -> get_event shows the ranked starts. Slot keys are candidate START times in the form YYYY-MM-DDTHH:MM (naive local time, no timezone). Once 2+ people answered, get_event.voteOptions lists the starts EVERYONE can make; people approve any number of them with vote_time, and the organiser settles it with decide_time (which locks picking and voting until decided with start=null). Identity: submit_availability and vote_time take an `identity` string: a random secret of at least 16 chars that you generate and keep per person (e.g. 32 hex chars) — never a plain user id or name, because anyone who guesses it can act as that person on every event. The server stores only its hash; the same identity later updates the same row, votes need an identity that already submitted at least one start, and names are display only (they may repeat). Keep the adminKey/adminUrl private: it is needed for update_event, remove_participant and decide_time.

Tools

8 advertised

create_event — Create event
Advertised by the server during the last successful anonymous check.

Create a sync.day availability poll and get its share link. Candidate days run from startDate to endDate (inclusive; or give days instead). Each day offers candidate START times from hourFrom, every startStepMinutes, as long as start + durationMinutes <= hourTo. Returns slug, public url (share this), adminUrl and adminKey (keep private; needed for update_event / remove_participant). Example: 周六周日下午聚餐 3 小时 -> {title:'周末聚餐', startDate:'2026-09-05', endDate:'2026-09-06', hourFrom:13, hourTo:18, durationMinutes:180, startStepMinutes:60}.

create_event input schema
{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "title",
    "startDate",
    "hourFrom",
    "hourTo",
    "durationMinutes"
  ],
  "properties": {
    "days": {
      "type": "integer",
      "maximum": 21,
      "minimum": 1,
      "description": "Number of consecutive days from startDate (1-21); alternative to endDate."
    },
    "title": {
      "type": "string",
      "maxLength": 60,
      "minLength": 1,
      "description": "Event name, max 60 chars. e.g. 周末聚餐, Team sync"
    },
    "hourTo": {
      "type": "integer",
      "maximum": 24,
      "minimum": 1,
      "description": "End of each day's window, exclusive (1-24), must be > hourFrom. e.g. 22"
    },
    "endDate": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
      "description": "Last candidate day, inclusive, YYYY-MM-DD (same as startDate for a single day; at most 21 days). Give this or days; endDate wins when both are set."
    },
    "hourFrom": {
      "type": "integer",
      "maximum": 23,
      "minimum": 0,
      "description": "Earliest hour of each day (0-23). e.g. 9"
    },
    "question": {
      "type": "string",
      "maxLength": 200,
      "description": "Optional prompt shown to participants, max 200 chars. e.g. 哪天晚上有空？"
    },
    "startDate": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
      "description": "First candidate day, YYYY-MM-DD. e.g. 2026-09-05"
    },
    "durationMinutes": {
      "anyOf": [
        {
          "type": "number",
          "const": 30
        },
        {
          "type": "number",
          "const": 60
        },
        {
          "type": "number",
          "const": 90
        },
        {
          "type": "number",
          "const": 120
        },
        {
          "type": "number",
          "const": 180
        },
        {
          "type": "number",
          "const": 240
        },
        {
          "type": "number",
          "const": 480
        }
      ],
      "description": "Event length in minutes. One of 30, 60, 90, 120, 180, 240, 480."
    },
    "startStepMinutes": {
      "anyOf": [
        {
          "type": "number",
          "const": 30
        },
        {
          "type": "number",
          "const": 60
        }
      ],
      "default": 60,
      "description": "Gap between candidate start times in minutes: 30 or 60 (default 60)."
    }
  }
}
create_event annotations
{
  "readOnlyHint": false,
  "openWorldHint": false,
  "idempotentHint": false,
  "destructiveHint": false
}
parse_event_text — Parse event text
Advertised by the server during the last successful anonymous check.
Advertised read-onlyOpen-world

Turn a natural-language sentence (Chinese works best) into create_event input using sync.day's AI parser. Does NOT create anything; review the result, then call create_event. Example: '下周六或周日下午聚餐，大概 3 小时'.

parse_event_text input schema
{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "text"
  ],
  "properties": {
    "text": {
      "type": "string",
      "maxLength": 300,
      "minLength": 1,
      "description": "One sentence describing the event, max 300 chars."
    },
    "today": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
      "description": "Reference date for relative words like 明天/下周, YYYY-MM-DD. Defaults to today in Asia/Shanghai."
    }
  }
}
parse_event_text annotations
{
  "readOnlyHint": true,
  "openWorldHint": true
}
get_event — Get event
Advertised by the server during the last successful anonymous check.
Advertised read-only

Read an event: settings, every candidate start key per day (startOptions), who has answered (participants with their start keys; names may repeat), the top 10 start times by head-count (ranked), the starts EVERYONE with picks can make with their votes (voteOptions), each person's vote (votes) and decidedStart. No key needed.

get_event input schema
{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "slug"
  ],
  "properties": {
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    }
  }
}
get_event annotations
{
  "readOnlyHint": true,
  "openWorldHint": false
}
submit_availability — Submit availability
Advertised by the server during the last successful anonymous check.

Save (or replace) one person's availability: the candidate start keys they can make, from get_event.startOptions. The person is identified by `identity`, not by name: the same identity later overwrites the same row (and can rename it), a different identity with the same name is a second participant. Keys outside the event's start options are rejected. Returns the updated ranking.

submit_availability input schema
{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "slug",
    "identity",
    "name",
    "starts"
  ],
  "properties": {
    "name": {
      "type": "string",
      "maxLength": 20,
      "minLength": 1,
      "description": "Display name, 1-20 chars, may repeat. e.g. 小明"
    },
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "starts": {
      "type": "array",
      "items": {
        "type": "string",
        "pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}$"
      },
      "maxItems": 1008,
      "description": "Start keys like 2026-09-05T14:00. Empty array clears this person's picks."
    },
    "identity": {
      "type": "string",
      "maxLength": 256,
      "minLength": 16,
      "description": "Random secret for this person that you generate and keep per person, 16-256 chars (e.g. 32 hex chars; NOT a plain user id or name, since anyone who guesses it can act as them). Same identity = same participant; the server stores only a hash. Example: 3f9a1c77b2e04d5e8a61f0c9d2b7e415"
    }
  }
}
submit_availability annotations
{
  "readOnlyHint": false,
  "openWorldHint": false,
  "idempotentHint": true,
  "destructiveHint": false
}
remove_participant — Remove participant
Advertised by the server during the last successful anonymous check.
Advertised destructive

Organiser only: remove one participant by name (the oldest row with that name when it repeats), together with their vote. Requires the adminKey from create_event.

remove_participant input schema
{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "slug",
    "name",
    "adminKey"
  ],
  "properties": {
    "name": {
      "type": "string",
      "maxLength": 20,
      "minLength": 1,
      "description": "Exact participant name to remove."
    },
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "adminKey": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{12}(?:[A-Za-z0-9_-]{12})?$",
      "description": "Organiser key returned by create_event (the ?key= part of adminUrl)."
    }
  }
}
remove_participant annotations
{
  "readOnlyHint": false,
  "openWorldHint": false,
  "idempotentHint": true,
  "destructiveHint": true
}
update_event — Update event
Advertised by the server during the last successful anonymous check.

Organiser only: change any event settings (same fields and rules as create_event; omitted fields keep their current value; endDate wins over days). Existing picks are kept; those no longer valid starts are just hidden.

update_event input schema
{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "slug",
    "adminKey"
  ],
  "properties": {
    "days": {
      "type": "integer",
      "maximum": 21,
      "minimum": 1,
      "description": "Number of consecutive days from startDate (1-21); alternative to endDate."
    },
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "title": {
      "type": "string",
      "maxLength": 60,
      "minLength": 1,
      "description": "Event name, max 60 chars. e.g. 周末聚餐, Team sync"
    },
    "hourTo": {
      "type": "integer",
      "maximum": 24,
      "minimum": 1,
      "description": "End of each day's window, exclusive (1-24), must be > hourFrom. e.g. 22"
    },
    "endDate": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
      "description": "Last candidate day, inclusive, YYYY-MM-DD (same as startDate for a single day; at most 21 days). Give this or days; endDate wins when both are set."
    },
    "adminKey": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{12}(?:[A-Za-z0-9_-]{12})?$",
      "description": "Organiser key returned by create_event (the ?key= part of adminUrl)."
    },
    "hourFrom": {
      "type": "integer",
      "maximum": 23,
      "minimum": 0,
      "description": "Earliest hour of each day (0-23). e.g. 9"
    },
    "question": {
      "type": "string",
      "maxLength": 200,
      "description": "Optional prompt shown to participants, max 200 chars. e.g. 哪天晚上有空？"
    },
    "startDate": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}$",
      "description": "First candidate day, YYYY-MM-DD. e.g. 2026-09-05"
    },
    "durationMinutes": {
      "anyOf": [
        {
          "type": "number",
          "const": 30
        },
        {
          "type": "number",
          "const": 60
        },
        {
          "type": "number",
          "const": 90
        },
        {
          "type": "number",
          "const": 120
        },
        {
          "type": "number",
          "const": 180
        },
        {
          "type": "number",
          "const": 240
        },
        {
          "type": "number",
          "const": 480
        }
      ],
      "description": "Event length in minutes. One of 30, 60, 90, 120, 180, 240, 480."
    },
    "startStepMinutes": {
      "anyOf": [
        {
          "type": "number",
          "const": 30
        },
        {
          "type": "number",
          "const": 60
        }
      ],
      "default": 60,
      "description": "Gap between candidate start times in minutes: 30 or 60 (default 60)."
    }
  }
}
update_event annotations
{
  "readOnlyHint": false,
  "openWorldHint": false,
  "idempotentHint": true,
  "destructiveHint": false
}
vote_time — Approve start times
Advertised by the server during the last successful anonymous check.

Approval voting: set every start one person accepts (replaces their earlier approvals; an empty list clears them). The voter is the `identity` used in submit_availability and must have at least one start saved. Only keys listed in get_event.voteOptions are accepted; the error lists the current options otherwise. Rejected once the organiser decided. Example: {slug:'calm-otter-4821', identity:'3f9a1c77b2e04d5e8a61f0c9d2b7e415', starts:['2026-09-05T15:00','2026-09-06T10:00']}. `start` is shorthand for a single-item `starts`.

vote_time input schema
{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "slug",
    "identity"
  ],
  "properties": {
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "start": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}$",
      "description": "Shorthand for starts: [start]"
    },
    "starts": {
      "type": "array",
      "items": {
        "type": "string",
        "pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}$",
        "description": "Start key, e.g. 2026-09-05T15:00"
      },
      "maxItems": 500,
      "description": "All start keys this person accepts (from get_event.voteOptions); [] clears their approvals"
    },
    "identity": {
      "type": "string",
      "maxLength": 256,
      "minLength": 16,
      "description": "Random secret for this person that you generate and keep per person, 16-256 chars (e.g. 32 hex chars; NOT a plain user id or name, since anyone who guesses it can act as them). Same identity = same participant; the server stores only a hash. Example: 3f9a1c77b2e04d5e8a61f0c9d2b7e415"
    }
  }
}
vote_time annotations
{
  "readOnlyHint": false,
  "openWorldHint": false,
  "idempotentHint": true,
  "destructiveHint": false
}
decide_time — Decide the time
Advertised by the server during the last successful anonymous check.

Organiser only: settle on a start time (locks availability picking and voting; the page shows 已定). Pass start=null to reopen. Requires the adminKey from create_event.

decide_time input schema
{
  "type": "object",
  "$schema": "https://json-schema.org/draft/2020-12/schema",
  "required": [
    "slug",
    "adminKey",
    "start"
  ],
  "properties": {
    "slug": {
      "type": "string",
      "pattern": "^(?:[a-z]{3,7}-[a-z]{3,7}(?:-\\d{2}|-\\d{4})?|[A-Za-z0-9_-]{10})$",
      "description": "Event slug from the URL, e.g. calm-otter-4821 (sync.day/calm-otter-4821)"
    },
    "start": {
      "anyOf": [
        {
          "type": "string",
          "pattern": "^\\d{4}-\\d{2}-\\d{2}T\\d{2}:\\d{2}$"
        },
        {
          "type": "null"
        }
      ],
      "description": "A candidate start key of the event (normally one of voteOptions), or null to reopen."
    },
    "adminKey": {
      "type": "string",
      "pattern": "^[A-Za-z0-9_-]{12}(?:[A-Za-z0-9_-]{12})?$",
      "description": "Organiser key returned by create_event (the ?key= part of adminUrl)."
    }
  }
}
decide_time annotations
{
  "readOnlyHint": false,
  "openWorldHint": false,
  "idempotentHint": true,
  "destructiveHint": false
}

Prompts

Not advertised

No prompt definitions available.

Resources

Not advertised

No resource definitions available.

90-day uptime

A lightweight connection check about every six hours, sampled on hosts with many listings. It shows the server answered, not that its tools work.

Too few checks for a percentage yet (1 of 1 answered).

  1. 2026-11-07: 1 of 1 checks answered

30-day availability

Aggregated from read-only remote checks; this is not a tool-execution or security guarantee.

Successful checks
1 of 1 (100%)
Average latency
797 ms
95th percentile latency
797 ms

Maintenance history

Public check and source-refresh events. Editorial and ownership records remain private.

  • · probe · passed · 797 ms · metadata changed · 8 tool(s)

Connect from your client

Each snippet registers the same endpoint; pick the client you use.

This server is operated by the named third party. Listing and endpoint checks are not an endorsement or a security audit. Review the operator's permissions, terms, and data handling before connecting. How listings are checked and corrected.

Claude Code

Run this once in a terminal. It registers the remote server. Use --scope project to write .mcp.json for the repo.
Claude Code configuration
claude mcp add --transport http sync-day-mcp https://sync.day/mcp/mcp

Codex

Run this once. Codex stores MCP servers in ~/.codex/config.toml (or .codex/config.toml in a trusted project).
Codex configuration
codex mcp add sync-day-mcp --url https://sync.day/mcp/mcp

Cursor

Merge this server into .cursor/mcp.json in your project, then enable sync-day-mcp in your MCP settings.
Cursor configuration
{
  "mcpServers": {
    "sync-day-mcp": {
      "url": "https://sync.day/mcp/mcp"
    }
  }
}

Cline

Merge this into cline_mcp_settings.json (Cline → MCP Servers → Configure).
Cline configuration
{
  "mcpServers": {
    "sync-day-mcp": {
      "type": "streamableHttp",
      "url": "https://sync.day/mcp/mcp",
      "disabled": false
    }
  }
}

VS Code

Merge this server into .vscode/mcp.json. Use MCP: List Servers to start sync-day-mcp and inspect its tools.
VS Code configuration
{
  "servers": {
    "sync-day-mcp": {
      "type": "http",
      "url": "https://sync.day/mcp/mcp"
    }
  }
}

Gemini CLI

Run this once. It writes .gemini/settings.json in the current project; pass --scope user for ~/.gemini/settings.json.
Gemini CLI configuration
gemini mcp add --transport http sync-day-mcp https://sync.day/mcp/mcp

Claude Desktop

Open Claude Settings > Connectors > Add custom connector, enter this server URL and enable it for the conversation. This is a manual remote-connector handoff, not a desktop JSON configuration.
Claude Desktop configuration
https://sync.day/mcp/mcp

Windsurf

Merge this into ~/.codeium/windsurf/mcp_config.json, then refresh MCP in Cascade. Windsurf remote servers use serverUrl, not url.
Windsurf configuration
{
  "mcpServers": {
    "sync-day-mcp": {
      "serverUrl": "https://sync.day/mcp/mcp"
    }
  }
}

Let your agent find its tools

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