I-Bond Rate Grounding Data

Overview

I-Bond Rates pulls data from the US Treasury Fiscal Data API. The composite rate consists of a fixed rate (set at purchase, never changes) plus an inflation rate (adjusts every May and November based on CPI). Historical rate data is available back to 1998.

Live Test I-Bond Rate Grounding Data Source →

The tool

Once your client is connected to the VerveContext server, this appears in its tool list as I-BondRateGroundingData. It is read-only and open-world — it fetches and never mutates anything on your side — so most clients call it without asking you to confirm.

Tool call

{
  "name": "I-BondRateGroundingData",
  "arguments": {}
}

Connecting

One server URL covers every source in the catalog, including this one. Authorization is OAuth: the client opens a browser once, and there is no key to paste into a config file.

{
  "mcpServers": {
    "vervecontext": {
      "url": "https://api.vervecontext.com/v1/mcp"
    }
  }
}

Per-client setup — Claude, Cursor, VS Code, ChatGPT — is on the MCP setup page.

Arguments

These are the properties on the tool's inputSchema, so a well-behaved client validates them before the call is made. Premium arguments are accepted on every plan but only take effect on plans that include them.

Argument	Type	Description
`period`OptionalPremium	string	Specific issue period to lookup (YYYY-MM format, e.g., 2024-11). Omit for current rates.

What the model gets back

The result carries a structuredContent object matching the tool's declared outputSchema, so a client reads fields without parsing prose. status is "ok" and error is null on success; a null field means the value was not available for that input, not that the call failed.

Result

{
  "status": "ok",
  "error": null,
  "data": {
    "period": "2026-10",
    "compositeRate": 4.26,
    "fixedRate": 0.9,
    "inflationRate": 1.67,
    "purchaseLimit": 10000,
    "minimumHoldingPeriod": "1 year",
    "earlyRedemptionPenalty": "Last 3 months interest if redeemed before 5 years",
    "taxAdvantages": "Federal tax deferred until redemption; exempt from state/local tax; may be tax-free for education",
    "nextRateChange": "2026-11-01",
    "lastUpdated": "2026-09-01T15:00:29.761Z"
  }
}

Response fields

Paths are relative to data. Premium fields are absent rather than zeroed on plans that do not include them, so check for presence instead of comparing to 0.

Field	Type	Example	Description
`period`	string	`2026-10`	Issue period for the rate (YYYY-MM format)
`compositeRate`	number	`4.26`	Total annual interest rate combining fixed and inflation components
`fixedRate`	number	`0.9`	Fixed rate component (set at purchase, never changes)
`inflationRate`	number	`1.67`	Inflation rate component (adjusts every 6 months)
`purchaseLimit`	number	`10000`	Annual electronic purchase limit per person in dollars
`minimumHoldingPeriod`	string	`1 year`	Minimum time bond must be held before redemption
`earlyRedemptionPenalty`	string	`Last 3 months interest if redeemed before 5 years`	Penalty for redeeming before 5 years
`taxAdvantages`	string	`Federal tax deferred until redemption; exempt from state/local tax; may be tax-free for education`	Tax benefits of I-Bonds
`nextRateChange`	string	`2026-11-01`	Date of next scheduled I-Bond rate announcement
`lastUpdated`	string	`2026-09-01T15:00:29.761Z`	ISO 8601 timestamp of last data refresh

Why ground on it

A model can produce something that looks like this answer from its training data, and be confidently out of date or simply wrong. This source returns the current value in a shape you can check, which is the difference between an answer you can cite and one you have to hedge.

Point an evaluation at compositeRate: it is the field most worth pinning a claim to, and it is either present and current or absent — never plausibly invented.

Failure modes

Errors come back as tool errors carrying a sentence the model can act on, not a bare status code. Error handling covers the full list.

Status	What it means
`400` / `422`	The arguments did not validate. The message names the offending one.
`401`	The OAuth session is invalid or expired — reconnect the server.
`403`	Blocked by a key restriction or an IP allow-list. Never a bad identity.
`404`	This source is not part of VerveContext. Check the catalog.
`429`	Out of credits, or a brief rate limit. The message tells them apart.

A call costs 2 credits each time the tool actually runs; a model that reasons about the tool without calling it costs nothing.

Use cases

Investment Research: Track I-Bond rates to optimize purchase timing around rate changes
Financial Planning: Factor I-Bond rates into inflation-protected savings strategies
Rate Tracking: Monitor I-Bond composite, fixed, and inflation rate components over time
Historical Analysis: Analyze historical I-Bond rates back to 1998 for trend research

Other ways to use I-Bond Rate Grounding Data

Set up I-Bond Rate Grounding Data on VerveContext, or reach the same source a different way. Your VerveContext account and credits work on all of them — one key, one balance.

Call it as a REST APIOne HTTPS endpoint and an x-api-key header, with SDKs for Node, Python and .NET.APIVerve →Reference →

Give it to an AI agentConnect over MCP and your agent calls it as a native tool — Claude, Cursor, ChatGPT.VerveKit →Reference →

Google Sheets or ExcelA =VERVE() formula fills a column — no script, no export, recalculates in place.VerveSheets →Reference →