I Bond Rate MCP

io.github.theluckystrikePublished by GitHub account theluckystrikev1.0.0Updated Nov 5, 2026

Current I bond rate, what your I bond earns by issue month, and value estimates from TreasuryDirect.

VerifiedStreamable HTTPWeb executableFinanceData & Analytics

Overview

AI-generated overview

Remote MCP server that gives an assistant current US Series I savings bond rates from TreasuryDirect, per-bond rates by issue month, and value estimates.

What you can do
  • Look up the current I bond composite, fixed and semiannual inflation rate, issue window and next announcement date
  • Get the fixed rate, current 6-month earnings rate, rate-change months and full rate history for a bond bought in a given month
  • Estimate a bond's value and redemption value after the 3-month penalty for a given issue month and amount
  • Apply the Treasury composite-rate formula to hypothetical fixed and inflation rates for predictions
  • Retrieve every fixed, semiannual inflation and composite rate announced since September 1998
When to use it
Useful when someone asks what I bonds pay now, what an existing I bond bought in a specific month is earning, or what a holding is worth and would redeem for. Also handy for hypothetical rate calculations, since the current rates postdate most model training data.
Requirements
A remote streamable HTTP endpoint; no API key, token or sign-up is needed. The README also mentions a local npm option, but that package is not published yet and would need Node 20 or newer. Network access to the hosted endpoint and, for live rates, to TreasuryDirect.
Before you install
Read-only: it does not access a TreasuryDirect account and handles neither EE bonds nor taxes. Value figures are estimates per $25 with semiannual compounding and can differ by cents from Treasury values. Per-bond schedules use a built-in rate chart, and the hosted server falls back to that chart when TreasuryDirect does not respond, so results may lag the live page; each result reports which source was used.

Installation

In SourceWeft

  1. Open I Bond Rate MCP in the dashboard and add it to a workspace.
  2. Enable the server for the chats that should use its tools.

Web executable via Streamable HTTP. Remote servers run from the web runtime once configured in a workspace.

Use with an agent

Paste this prompt into Claude Code, Codex, Cursor or another agent — or into SourceWeft chat. The agent reads this server's install guide, shows you its publisher, endpoint and sign-in, and adds it to your client once you agree. Keys never go into a command.

Read https://sourceweft.com/mcp/io.github.theluckystrike%2Fi-bond-rate-mcp/install.md and connect the MCP server it describes to my client. Before changing any config, show me its publisher, endpoint and sign-in method and wait for my OK. Never put an API key in a command or in a file I would commit; ask me where it should come from.

Read the install guide the agent follows

Other MCP clients

Add this to your client's mcpServers config.

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

README

i-bond-rate-mcp

Current I bond rate for AI assistants, and the rate your own I bond earns now. I bonds bought from November 1, 2026 to April 30, 2027 earn 5.51 percent, with a 1.40 percent fixed rate.

This is a Model Context Protocol (MCP) server. It reads the current rate from TreasuryDirect at call time and carries every rate since September 1998 from the TreasuryDirect rate chart. It needs no API key.

Tools

ToolWhat it returns
get_current_i_bond_rateComposite, fixed and semiannual inflation rate for I bonds bought now, the issue window, the next announcement date and the purchase and redemption rules.
get_i_bond_rate_for_issue_dateFor a bond bought in a given month: its fixed rate, the rate it earns in the current 6-month period, the two months its rate changes, whether it can be cashed and every rate period since issue.
estimate_i_bond_valueEstimated value for an issue month and amount, with all interest and after the 3-month penalty for bonds under 5 years.
calculate_i_bond_composite_rateThe Treasury formula for any fixed rate and semiannual inflation rate, for predictions.
get_i_bond_rate_historyEvery fixed rate and semiannual inflation rate since September 1998, newest first.

Every result has structured JSON, a one-paragraph summary, as_of, source (the TreasuryDirect page or rate chart) and more (a page on mcpstamp.com).

What it knows that your model does not

  • The November 2026 rates (5.51 percent composite, 1.40 percent fixed, 2.04 percent semiannual inflation). Treasury announced them on November 1, 2026.
  • That an existing bond does not earn the new-bond rate. It keeps its own fixed rate and gets a new inflation rate every 6 months from its issue month, so a bond bought in April 2022 earns 3.34 percent from October 2026 while a bond bought in January 2023 earns 3.75 percent until January 2027.
  • The exact rounding and the zero floor. The formula reproduces all 1,711 composite rates in the Treasury chart.

Install

Hosted (Claude.ai custom connector, ChatGPT developer mode)

Paste this URL. No token, no sign-up. It works now.

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

Claude Code

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

Claude Desktop

Claude Desktop adds remote servers under Settings, Connectors, Add custom connector. Paste the URL above.

Cursor

Add to ~/.cursor/mcp.json:

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

VS Code

Add to .vscode/mcp.json:

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

Local stdio (after npm release)

The npm package is not published yet. After it is, run it locally with Node 20 or newer:

claude mcp add i-bond -- npx -y i-bond-rate-mcp

Example prompts

  • "What is the I bond rate right now?"
  • "What is the I bond fixed rate for November 2026?"
  • "I bought I bonds in April 2022. What rate are they earning now?"
  • "What is $10,000 of I bonds bought in January 2023 worth today, and what would I get if I cash them?"
  • "If May 2027 inflation is 1.5 percent and the fixed rate stays at 1.40, what would the I bond rate be?"

Data sources

Full list with fetch dates in DATA_SOURCES.md.

Limitations

  • Value is an estimate per $25 with semiannual compounding. Treasury values can differ by cents. Your TreasuryDirect account and the Savings Bond Calculator are the record.
  • Rates after April 2027 are not known until Treasury announces them on May 1, 2027. The current-rate tool reads the live page, but the per-bond schedule uses the built-in chart until this server is updated.
  • TreasuryDirect did not answer the hosted Worker on 2026-11-05, so the hosted server falls back to the built-in rate chart after a few seconds. Every result says which source it used in rate_source.
  • It does not read your TreasuryDirect account and does not handle EE bonds or taxes.

More

More MCP servers that answer questions your assistant cannot answer alone are on mcpstamp.com.

Part of the Zovo MCP collection: https://mcp.zovo.one

Built by theluckystrike.

Development

npm installnpm test                              # builds, then runs the fixture tests and an offline stdio testnode scripts/stdio-transcript.mjs     # live stdio round trip, writes .live/stdio-transcript.jsonl

License

MIT

Source: README.md at commit c73af2b

Tools

5

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. 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.

Takes no parameters.

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. Computed from the TreasuryDirect rate chart effective November 1, 2026.

Parametersas_of_monthissue_monthrequired

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. Uses semiannual compounding per $25 with the TreasuryDirect rates. An estimate; Treasury values can differ by cents.

Parametersamountrequiredas_of_monthissue_monthrequired

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.

Parametersfixed_raterequiredsemiannual_inflation_raterequired

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.

Parameterslimit

Version history

1
  1. v1.0.0LatestNov 5, 2026

Score

100% of the applicable checks met

How complete this listing is, computed from the registry entry, the endpoint and public sources. Not a rating of the server and not a statement that it is safe or working today: reachability is a dated check, and no installs or reviews go into the score.

  • Reached in the last 30 daysRequired25 pts
  • Auth declaredRequired10 pts
  • Tools listedRequired15 pts
  • DescriptionRequired15 pts
  • Logo10 pts
  • Documentation15 pts
  • License10 pts