congressgov-mcp-server

Congress.gov Enacted Laws

congressgov_enacted_laws

Read-onlyIdempotent

Browse enacted public and private laws from Congress.gov by congress and law type ('pub' for public laws, 'priv' for private). 'list' filters by enactment status and law type — the discovery path 'bill_lookup' does not offer. 'get' returns the origin bill record (sponsor, actions, summaries, text), with the public/private law citation on the bill's 'laws' array (e.g. {"number":"118-2","type":"Public Law"}).

Input Schema

Name	Required	Description
`limit`	No	Results per page (1-250).
`offset`	No	Pagination offset.
`lawType`	No	Law type — 'pub' (public laws, general application, most common) or 'priv' (private laws, specific individuals or entities). Required for 'get'.
`congress`	Yes	Congress number.
`lawNumber`	No	Law number, as carried by a 'list' row's `laws[].number` — either the full citation ('118-90', rendered as 'Public Law 118-90') or the portion after the hyphen ('90'); the prefix is the congress and must match `congress`. Not the row's own `number`, which is the origin bill. Required for 'get'.
`operation`	Yes	Which data to retrieve.

Output Schema

Name	Required	Description
`law`	No	Dynamic upstream JSON record.
`data`	No	Result rows. Per-tool item shape is rendered in the markdown body.
`error`	No	Present when the call failed. Absent on success.
`notice`	No	Guidance when results are empty, a page is past the end, or a caveat applies.
`pagination`	No	Pagination metadata: total count and next offset.
`totalCount`	No	Total results across all pages.
`effectiveQuery`	No	The browse scope and applied filters.

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedNov 2, 2026

changedOutput schema / properties / error / properties / data / properties / reason / description

Previous value: -"Machine-readable failure mode. Declared by this tool: `not_found`: A requested bill, member, committee, report, vote, or nomination does not exist in Congress.gov. `rate_limited`: A process-local attempt budget or the shared upstream credential/IP quota was reached; upstream hourly limits vary and DEMO_KEY also has a daily quota. `invalid_request`: Congress.gov rejected the request as malformed — a bad date range or an identifier with an unexpected shape. `upstream_error`: Congress.gov returned an unexpected error (5xx or another non-2xx status). `upstream_timeout`: The Congress.gov request deadline expired or the upstream returned an HTTP timeout response. Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `not_found`: A requested bill, member, committee, report, vote, or nomination does not exist in Congress.gov. `rate_limited`: A process-local attempt budget or the shared upstream credential/IP quota was reached; upstream hourly limits vary and DEMO_KEY also has a daily quota. `invalid_request`: Congress.gov rejected the request as malformed — a bad date range or an identifier with an unexpected shape. `api_key_rejected`: The api.data.gov gateway rejected the server's configured CONGRESS_API_KEY (missing, invalid, disabled, unauthorized, or unverified); the gateway code is in data.upstreamCode. No change to the call's arguments can fix it. `upstream_error`: Congress.gov returned an unexpected error (5xx or another non-2xx status) or could not be reached, or the Senate LIS feed failed (5xx, a timeout, or a senate.gov HTTP 403 refusal, which carries retryable: false). `upstream_timeout`: A Congress.gov request or a congress.gov document fetch timed out or returned an HTTP timeout response, or the call's upstream requests could not finish inside its 50-second budget. Other values are possible when a failure originates below the handler."

changedOutput schema / properties / error / properties / data / properties / reason / examples

Previous value: -[
-  "not_found",
-  "rate_limited",
-  "invalid_request",
-  "upstream_error",
-  "upstream_timeout"
-]New value: +[
+  "not_found",
+  "rate_limited",
+  "invalid_request",
+  "api_key_rejected",
+  "upstream_error",
+  "upstream_timeout"
+]

Changed2 schema fields changedOct 13, 2026

changedOutput schema / properties / error / properties / data / properties / reason / description

Previous value: -"Machine-readable failure mode. Declared by this tool: `not_found`: A requested bill, member, committee, report, vote, or nomination does not exist in Congress.gov. `rate_limited`: The Congress.gov API rate limit (5,000 requests/hour per key) was exceeded. `invalid_request`: Congress.gov rejected the request as malformed — a bad date range or an identifier with an unexpected shape. `upstream_error`: Congress.gov returned an unexpected error (5xx or another non-2xx status). Other values are possible when a failure originates below the handler."New value: +"Machine-readable failure mode. Declared by this tool: `not_found`: A requested bill, member, committee, report, vote, or nomination does not exist in Congress.gov. `rate_limited`: A process-local attempt budget or the shared upstream credential/IP quota was reached; upstream hourly limits vary and DEMO_KEY also has a daily quota. `invalid_request`: Congress.gov rejected the request as malformed — a bad date range or an identifier with an unexpected shape. `upstream_error`: Congress.gov returned an unexpected error (5xx or another non-2xx status). `upstream_timeout`: The Congress.gov request deadline expired or the upstream returned an HTTP timeout response. Other values are possible when a failure originates below the handler."

changedOutput schema / properties / error / properties / data / properties / reason / examples

Previous value: -[
-  "not_found",
-  "rate_limited",
-  "invalid_request",
-  "upstream_error"
-]New value: +[
+  "not_found",
+  "rate_limited",
+  "invalid_request",
+  "upstream_error",
+  "upstream_timeout"
+]

Changed1 schema field changedAug 30, 2026

addedOutput schema / properties / law

Added value: +{
+  "additionalProperties": {},
+  "description": "Dynamic upstream JSON record.",
+  "properties": {},
+  "type": "object"
+}

Changed6 schema fields changedAug 25, 2026

changedInput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

addedInput schema / additionalProperties
```
Added value: +false
```

changedOutput schema / $schema

Previous value: -"http://json-schema.org/draft-07/schema#"New value: +"https://json-schema.org/draft/2020-12/schema"

addedOutput schema / anyOf

Added value: +[
+  {
+    "not": {
+      "required": [
+        "error"
+      ]
+    },
+    "required": [
+      "effectiveQuery",
+      "totalCount"
+    ]
+  },
+  {
+    "required": [
+      "error"
+    ]
+  }
+]

addedOutput schema / properties / error

Added value: +{
+  "additionalProperties": {},
+  "description": "Present when the call failed. Absent on success.",
+  "properties": {
+    "code": {
+      "description": "JSON-RPC error code for this failure.",
+      "maximum": 9007199254740991,
+      "minimum": -9007199254740991,
+      "type": "integer"
+    },
+    "data": {
+      "additionalProperties": {},
+      "properties": {
+        "reason": {
+          "description": "Machine-readable failure mode. Declared by this tool: `not_found`: A requested bill, member, committee, report, vote, or nomination does not exist in Congress.gov. `rate_limited`: The Congress.gov API rate limit (5,000 requests/hour per key) was exceeded. `invalid_request`: Congress.gov rejected the request as malformed — a bad date range or an identifier with an unexpected shape. `upstream_error`: Congress.gov returned an unexpected error (5xx or another non-2xx status). Other values are possible when a failure originates below the handler.",
+          "examples": [
+            "not_found",
+            "rate_limited",
+            "invalid_request",
+            "upstream_error"
+          ],
+          "type": "string"
+        },
+        "recovery": {
+          "additionalProperties": {},
+          "description": "Actionable next step for the caller.",
+          "properties": {
+            "hint": {
+              "type": "string"
+            }
+          },
+          "required": [
+            "hint"
+          ],
+          "type": "object"
+        },
+        "retryable": {
+          "description": "Whether retrying may succeed.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "message": {
+      "description": "Human-readable description of what went wrong.",
+      "type": "string"
+    }
+  },
+  "required": [
+    "code",
+    "message"
+  ],
+  "type": "object"
+}

removedOutput schema / required

Removed value: -[
-  "effectiveQuery",
-  "totalCount"
-]

Changed5 schema fields changedAug 17, 2026

addedInput schema / properties / lawNumber / anyOf

Added value: +[
+  {
+    "description": "Positive integer form (e.g. 90).",
+    "exclusiveMinimum": 0,
+    "maximum": 9007199254740991,
+    "type": "integer"
+  },
+  {
+    "description": "String form — the law number (\"90\") or the full citation (\"118-90\").",
+    "pattern": "^(?:\\d+-)?0*[1-9]\\d*$",
+    "type": "string"
+  }
+]

changedInput schema / properties / lawNumber / description

Previous value: -"Law number. Required for 'get'."New value: +"Law number, as carried by a 'list' row's `laws[].number` — either the full citation ('118-90', rendered as 'Public Law 118-90') or the portion after the hyphen ('90'); the prefix is the congress and must match `congress`. Not the row's own `number`, which is the origin bill. Required for 'get'."

removedInput schema / properties / lawNumber / exclusiveMinimum
```
Removed value: -0
```
removedInput schema / properties / lawNumber / maximum
```
Removed value: -9007199254740991
```
removedInput schema / properties / lawNumber / type
```
Removed value: -"integer"
```

Changed6 schema fields changedMay 30, 2026

removedOutput schema / description

Removed value: -"Detail-mode key 'law' carries: Origin bill record for `get`; absent for `list`. The bill's `laws` array carries the law citation."

addedOutput schema / properties / effectiveQuery

Added value: +{
+  "description": "The browse scope and applied filters.",
+  "type": "string"
+}

addedOutput schema / properties / notice

Added value: +{
+  "description": "Guidance when results are empty, a page is past the end, or a caveat applies.",
+  "type": "string"
+}

removedOutput schema / properties / query

Removed value: -{
-  "description": "Echo of the applied filters for list-mode queries. Rendered as the first line of the response.",
-  "type": "string"
-}

addedOutput schema / properties / totalCount

Added value: +{
+  "description": "Total results across all pages.",
+  "type": "number"
+}

addedOutput schema / required

Added value: +[
+  "effectiveQuery",
+  "totalCount"
+]

Changed4 schema fields changedMay 21, 2026

changedOutput schema / description

Previous value: -"Law data from Congress.gov API."New value: +"Detail-mode key 'law' carries: Origin bill record for `get`; absent for `list`. The bill's `laws` array carries the law citation."

addedOutput schema / properties / data

Added value: +{
+  "description": "Result rows. Per-tool item shape is rendered in the markdown body.",
+  "items": {
+    "additionalProperties": {},
+    "description": "Upstream JSON record. Per-tool item shape is rendered in the markdown body.",
+    "properties": {},
+    "type": "object"
+  },
+  "type": "array"
+}

addedOutput schema / properties / pagination

Added value: +{
+  "additionalProperties": false,
+  "description": "Pagination metadata: total count and next offset.",
+  "properties": {
+    "count": {
+      "description": "Total result count across all pages.",
+      "maximum": 9007199254740991,
+      "minimum": 0,
+      "type": "integer"
+    },
+    "nextOffset": {
+      "anyOf": [
+        {
+          "maximum": 9007199254740991,
+          "minimum": 0,
+          "type": "integer"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "description": "Offset to pass for the next page, or null when there are no more pages."
+    }
+  },
+  "required": [
+    "count"
+  ],
+  "type": "object"
+}

addedOutput schema / properties / query

Added value: +{
+  "description": "Echo of the applied filters for list-mode queries. Rendered as the first line of the response.",
+  "type": "string"
+}

Changed1 schema field changedMay 8, 2026

changedInput schema / properties / lawType / description

Previous value: -"Law type. Required for 'get'."New value: +"Law type — 'pub' (public laws, general application, most common) or 'priv' (private laws, specific individuals or entities). Required for 'get'."

First observedMar 28, 2026

TDQS

A4.3/5.0

Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds useful behavioral context by explaining that 'get' resolves back to the origin bill record and that the law citation lives in the bill's 'laws' array, which clarifies the tool's data model beyond the annotations.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Three tightly written sentences, front-loaded with the tool's purpose and sibling distinction. The parenthetical clarifications and citation example earn their space by disambiguating lawType and lawNumber.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

The description covers both operations, the key domain concepts (public/private laws, origin bill, laws array), and gives enough context to invoke the tool correctly. Because an output schema exists, it does not need to enumerate return fields in detail, and the remaining parameter details are fully documented in the schema.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the input schema already documents congress, lawType, lawNumber, limit, and offset thoroughly. The description reinforces the meaning of lawType and lawNumber with examples, but largely repeats what the schema provides rather than adding new parameter semantics.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description states a specific verb ('Browse') and resource ('enacted public and private laws'), and immediately distinguishes the tool from the sibling discovery path by naming 'bill_lookup'. An agent can tell what this tool does and how it differs without opening the schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

It explicitly contrasts 'list' with 'bill_lookup', noting that list filters by enactment status and law type where bill_lookup does not. It also explains what 'get' returns, though it does not explicitly state when to choose 'get' versus 'list' beyond the operation semantics already implied.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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