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I bond rate MCP server

The current Series I savings bond rate from TreasuryDirect, and the rate your own I bond earns by its issue month.

Connect free Source on GitHub

Free. No key, no sign-in, no paid tier. 5 tools.

Can Claude tell me the current I bond rate?

Connector URL

https://i-bond-rate-mcp.lipmichal.workers.dev/mcp

Paste it as a custom connector in Claude, or add it to Claude Code, Cursor or VS Code. Setup for each is below.

What it knows that a model doesn't

A model answers from training data. This server reads the source when you ask.

  • The composite, fixed and inflation rate for I bonds bought November 2026 to April 2027 (5.51 percent with a 1.40 percent fixed rate).
  • The rate an I bond you already own earns now, from its issue month, and every rate period since you bought it.
  • An estimate of what your I bonds are worth, before and after the 3-month penalty. It gives rates and math, not investment advice.

Sources TreasuryDirect "I bonds interest rates" page, read at call time, and the TreasuryDirect I bond rate chart effective November 1, 2026 as the built-in fallback.

Tools (5)

Read from the live server with tools/list on 2026-11-05.

ToolWhat it does
get_current_i_bond_rate Get current I bond rate. 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.
get_i_bond_rate_for_issue_date Get I bond rate for an issue date. 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.
estimate_i_bond_value Estimate I bond value. 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.
calculate_i_bond_composite_rate Calculate I bond composite rate. 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.
get_i_bond_rate_history Get I bond rate history. 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.

Connect it

One URL, no token. Pick your app.

Claude.ai and Claude Desktop

Open Settings, then Connectors, then Add custom connector. Paste the URL. Leave the OAuth fields empty. Save.

https://i-bond-rate-mcp.lipmichal.workers.dev/mcp

Claude Code

Run this in your terminal. Then run claude mcp list to check it.

claude mcp add --transport http i-bond-rate https://i-bond-rate-mcp.lipmichal.workers.dev/mcp

Cursor

Merge this into ~/.cursor/mcp.json (all projects) or .cursor/mcp.json (one project).

{
  "mcpServers": {
    "i-bond-rate": {
      "url": "https://i-bond-rate-mcp.lipmichal.workers.dev/mcp"
    }
  }
}

VS Code

Put this in .vscode/mcp.json. The top key is servers, not mcpServers.

{
  "servers": {
    "i-bond-rate": {
      "type": "http",
      "url": "https://i-bond-rate-mcp.lipmichal.workers.dev/mcp"
    }
  }
}

Things to ask

Paste one into a new chat after you connect.

Sourcegithub.com/theluckystrike/i-bond-rate-mcp

Questions

Is the i bond rate MCP server free?
Yes. The hosted URL is free and needs no token, key or account. The source is open on GitHub.
Why not just ask the model?
A model answers from its training data. That data stops at a cutoff date, and long sums can drift. This server reads its data or rules each time you ask, so the answer is current and exact.
Where does the data come from?
TreasuryDirect "I bonds interest rates" page, read at call time, and the TreasuryDirect I bond rate chart effective November 1, 2026 as the built-in fallback.
Which apps can use it?
Any MCP client that accepts a remote server URL: Claude.ai and Claude Desktop custom connectors, Claude Code, Cursor, VS Code and others. You can also run it locally with npx.

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