Koskamo

I Bond Rate MCP

An open-source MCP server that retrieves current Series I bond rates, calculates composite rates, estimates bond values including early-redemption penalties, and provides historical rate data sourced directly from TreasuryDirect.

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.

I Bond Rate MCP logo, by theluckystrikeCommunity listingStreamable HTTPNo sign-inEndpoint checked 2026-11-07Published by theluckystrike
MCP endpoint (Streamable HTTP)
https://i-bond-rate-mcp.lipmichal.workers.dev/mcp
Vendor documentation

What its tools do

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

Read-only (5)

5 of 5 have a description · 5 of 5 declare behavior hints · 4 of 4 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

  • Get the current I bond composite and fixed rates
  • Calculate the estimated value of I bonds by issue month
  • Retrieve historical fixed and inflation rates since 1998
  • Compute composite rates using the Treasury formula

Source and maintenance

Community listingRegistry 1.0.0
mcp-registry: io.github.theluckystrike/i-bond-rate-mcp@1.0.0Source repository
Maintenance checked

Protocol and capabilities

Server
i-bond-rate-mcp 1.0.0
MCP protocol negotiated in check
2025-11-25
Tools
5 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.

Series I savings bond rates from TreasuryDirect. The rate for I bonds bought November 1, 2026 to April 30, 2027 is 5.51 percent (fixed 1.40 percent, semiannual inflation 2.04 percent), announced after most model training data. Every older bond has its own fixed rate and changes rate every 6 months from its issue month; use get_i_bond_rate_for_issue_date for "what is my I bond earning now".

Tools

5 advertised

get_current_i_bond_rate — Get current I bond rate
Advertised by the server during the last successful anonymous check.
Advertised read-onlyOpen-world

Current Series I savings bond composite rate, fixed rate and semiannual inflation rate for new purchases, read at call time from the TreasuryDirect "I bonds interest rates" page with the built-in rate chart as fallback. November 2026 to April 2027: 5.51 percent with a 1.40 percent fixed rate. Also returns the next announcement date and the $10,000 limit, 12-month hold and 3-month penalty rules.

get_current_i_bond_rate input schema
{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "properties": {}
}
get_current_i_bond_rate annotations
{
  "title": "Current I bond rate",
  "readOnlyHint": true,
  "openWorldHint": true,
  "idempotentHint": true,
  "destructiveHint": false
}
get_i_bond_rate_for_issue_date — Get I bond rate for an issue date
Advertised by the server during the last successful anonymous check.
Advertised read-only

For an I bond bought in a given month: its fixed rate, the composite rate it earns in the current (or given) 6-month period, the months its rate changes, whether it can be cashed and the penalty, and every rate period since issue. Computed from the TreasuryDirect rate chart effective November 1, 2026.

get_i_bond_rate_for_issue_date input schema
{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "required": [
    "issue_month"
  ],
  "properties": {
    "as_of_month": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{1,2}(-\\d{1,2})?$",
      "description": "Month to evaluate, YYYY-MM. Default: the current month."
    },
    "issue_month": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{1,2}(-\\d{1,2})?$",
      "description": "Issue month of the bond as YYYY-MM, for example \"2023-01\". The issue date is the first of the month you bought it."
    }
  },
  "additionalProperties": false
}
get_i_bond_rate_for_issue_date annotations
{
  "title": "I bond rate by issue date",
  "readOnlyHint": true,
  "openWorldHint": false,
  "idempotentHint": true,
  "destructiveHint": false
}
estimate_i_bond_value — Estimate I bond value
Advertised by the server during the last successful anonymous check.
Advertised read-only

Estimate what I bonds are worth for an issue month and purchase amount at the start of a month: value with all interest and the redemption value after the 3-month penalty for bonds under 5 years. Uses semiannual compounding per $25 with the TreasuryDirect rates. An estimate; Treasury values can differ by cents.

estimate_i_bond_value input schema
{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "required": [
    "issue_month",
    "amount"
  ],
  "properties": {
    "amount": {
      "type": "number",
      "maximum": 10000000,
      "minimum": 25,
      "description": "Purchase price in dollars, for example 10000."
    },
    "as_of_month": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{1,2}(-\\d{1,2})?$",
      "description": "Month to evaluate, YYYY-MM. Default: the current month."
    },
    "issue_month": {
      "type": "string",
      "pattern": "^\\d{4}-\\d{1,2}(-\\d{1,2})?$",
      "description": "Issue month of the bond as YYYY-MM, for example \"2023-01\". The issue date is the first of the month you bought it."
    }
  },
  "additionalProperties": false
}
estimate_i_bond_value annotations
{
  "title": "I bond value estimate",
  "readOnlyHint": true,
  "openWorldHint": false,
  "idempotentHint": true,
  "destructiveHint": false
}
calculate_i_bond_composite_rate — Calculate I bond composite rate
Advertised by the server during the last successful anonymous check.
Advertised read-only

Apply the Treasury formula fixed + 2 x semiannual inflation + fixed x semiannual inflation, rounded to 0.01 percent with a floor of zero. Use it for rate predictions.

calculate_i_bond_composite_rate input schema
{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "required": [
    "fixed_rate",
    "semiannual_inflation_rate"
  ],
  "properties": {
    "fixed_rate": {
      "type": "number",
      "maximum": 10,
      "minimum": 0,
      "description": "Fixed rate in percent, for example 1.4."
    },
    "semiannual_inflation_rate": {
      "type": "number",
      "maximum": 10,
      "minimum": -10,
      "description": "Semiannual inflation rate in percent, for example 2.04."
    }
  },
  "additionalProperties": false
}
calculate_i_bond_composite_rate annotations
{
  "title": "Composite rate formula",
  "readOnlyHint": true,
  "openWorldHint": false,
  "idempotentHint": true,
  "destructiveHint": false
}
get_i_bond_rate_history — Get I bond rate history
Advertised by the server during the last successful anonymous check.
Advertised read-only

Fixed rate for new bonds, semiannual inflation rate and composite rate for every May and November announcement since September 1998, newest first, from the TreasuryDirect rate chart.

get_i_bond_rate_history input schema
{
  "type": "object",
  "$schema": "http://json-schema.org/draft-07/schema#",
  "properties": {
    "limit": {
      "type": "integer",
      "maximum": 60,
      "minimum": 1,
      "description": "How many announcements, newest first. Default 20."
    }
  },
  "additionalProperties": false
}
get_i_bond_rate_history annotations
{
  "title": "I bond rate history",
  "readOnlyHint": true,
  "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
442 ms
95th percentile latency
442 ms

Maintenance history

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

  • · probe · passed · 442 ms · metadata changed · 5 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 i-bond-rate-mcp https://i-bond-rate-mcp.lipmichal.workers.dev/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 i-bond-rate-mcp --url https://i-bond-rate-mcp.lipmichal.workers.dev/mcp

Cursor

Merge this server into .cursor/mcp.json in your project, then enable i-bond-rate-mcp in your MCP settings.
Cursor configuration
{
  "mcpServers": {
    "i-bond-rate-mcp": {
      "url": "https://i-bond-rate-mcp.lipmichal.workers.dev/mcp"
    }
  }
}

Cline

Merge this into cline_mcp_settings.json (Cline → MCP Servers → Configure).
Cline configuration
{
  "mcpServers": {
    "i-bond-rate-mcp": {
      "type": "streamableHttp",
      "url": "https://i-bond-rate-mcp.lipmichal.workers.dev/mcp",
      "disabled": false
    }
  }
}

VS Code

Merge this server into .vscode/mcp.json. Use MCP: List Servers to start i-bond-rate-mcp and inspect its tools.
VS Code configuration
{
  "servers": {
    "i-bond-rate-mcp": {
      "type": "http",
      "url": "https://i-bond-rate-mcp.lipmichal.workers.dev/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 i-bond-rate-mcp https://i-bond-rate-mcp.lipmichal.workers.dev/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://i-bond-rate-mcp.lipmichal.workers.dev/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": {
    "i-bond-rate-mcp": {
      "serverUrl": "https://i-bond-rate-mcp.lipmichal.workers.dev/mcp"
    }
  }
}

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