Current I bond rate, what your I bond earns by issue month, and value estimates from TreasuryDirect.
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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.
Fixed rate in percent, for example 1.4.
Semiannual inflation rate in percent, for example 2.04.
Pick your client. Values in capitals, like YOUR_TOKEN, are yours to fill in.
Run in a terminal
claude mcp add --transport http i-bond-rate-mcp https://i-bond-rate-mcp.lipmichal.workers.dev/mcp
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.
| Argument | Type | Description |
|---|---|---|
| fixed_rate* | number | Fixed rate in percent, for example 1.4. |
| semiannual_inflation_rate* | number | Semiannual inflation rate in percent, for example 2.04. |
{
"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
}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 $25 with the TreasuryDirect rates. An estimate; Treasury values can differ by cents.
| Argument | Type | Description |
|---|---|---|
| amount* | number | Purchase price in dollars, for example 10000. |
| as_of_month | string | Month to evaluate, YYYY-MM. Default: the current month. |
| issue_month* | string | Issue month of the bond as YYYY-MM, for example "2023-01". The issue date is the first of the month you bought it. |
{
"type": "object",
"$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
}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 $10,000 limit, 12-month hold and 3-month penalty rules.
No arguments.
{
"type": "object",
"$schema": "http://json-schema.org/draft-07/schema#",
"properties": {}
}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.
| Argument | Type | Description |
|---|---|---|
| as_of_month | string | Month to evaluate, YYYY-MM. Default: the current month. |
| issue_month* | string | Issue month of the bond as YYYY-MM, for example "2023-01". The issue date is the first of the month you bought it. |
{
"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})?$",
"description": "Issue month of the bond as YYYY-MM, for example \"2023-01\". The issue date is the first of the month you bought it."
}
},
"additionalProperties": false
}Fixed rate for new bonds, semiannual inflation rate and composite rate for every May and November announcement since September 1998, newest first, from the TreasuryDirect rate chart.
| Argument | Type | Description |
|---|---|---|
| limit | integer | How many announcements, newest first. Default 20. |
{
"type": "object",
"$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
}We read every tool's name, description and inputs the way the model will, looking for instructions hidden from you. A clean result means no warning signs, not a guarantee. Scanned Nov 5, 2026.