congressgov-mcp-server

Congress.gov Member Lookup

congressgov_member_lookup

Read-onlyIdempotent

Discover congressional members and their legislative activity. No name search. For 'list', filter by stateCode (optionally with district), by congress, or by both together (e.g., 118th Congress + CA, or CA district 12 in the 118th). Add currentMember=true to restrict to currently serving members. Once you have a bioguideId, use 'get' for full profile or 'sponsored'/'cosponsored' for their legislative portfolio.

Input Schema

Name	Required	Description
`limit`	No	Results per page (1-250).
`offset`	No	Pagination offset.
`congress`	No	Congress number to filter by.
`district`	No	Congressional district number. Requires stateCode. Use 0 for at-large.
`operation`	Yes	Which data to retrieve.
`stateCode`	No	Two-letter state code (e.g., 'CA', 'TX').
`bioguideId`	No	Unique member identifier (e.g., 'P000197'). Required for get/sponsored/cosponsored.
`currentMember`	No	Filter to currently serving members. Omit to include both current and former members.

Output Schema

Name	Required	Description
`data`	No	Result rows. Per-tool item shape is rendered in the markdown body.
`error`	No	Present when the call failed. Absent on success.
`member`	No	Dynamic upstream JSON record.
`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"
+]

Changed5 schema fields changedAug 30, 2026
- addedInput schema / properties / bioguideId / pattern
```
Added value: +"^[A-Za-z]\\d{6}$"
```
- removedInput schema / properties / stateCode / maxLength
```
Removed value: -2
```
- removedInput schema / properties / stateCode / minLength
```
Removed value: -2
```
- addedInput schema / properties / stateCode / pattern
```
Added value: +"^[A-Za-z]{2}$"
```
- addedOutput schema / properties / member
```
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"
-]

Changed6 schema fields changedMay 30, 2026

removedOutput schema / description

Removed value: -"Detail-mode key 'member' carries: Member profile for `get` (name, state, terms, party history, leadership, legislation counts); absent for `list`, `sponsored`, `cosponsored`."

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: -"Member data from Congress.gov API."New value: +"Detail-mode key 'member' carries: Member profile for `get` (name, state, terms, party history, leadership, legislation counts); absent for `list`, `sponsored`, `cosponsored`."

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"
+}

Changed3 schema fields changedApr 21, 2026

removedOutput schema / properties / data

Removed value: -{
-  "description": "Paginated member or legislation results. Preserves upstream item shapes.",
-  "items": {},
-  "type": "array"
-}

removedOutput schema / properties / member

Removed value: -{
-  "additionalProperties": {},
-  "description": "Member profile detail when operation=\"get\".",
-  "propertyNames": {
-    "type": "string"
-  },
-  "type": "object"
-}

removedOutput schema / properties / pagination

Removed value: -{
-  "additionalProperties": false,
-  "description": "Pagination metadata for list, sponsored, and cosponsored operations.",
-  "properties": {
-    "count": {
-      "description": "Total number of matching members or bills.",
-      "maximum": 9007199254740991,
-      "minimum": 0,
-      "type": "integer"
-    },
-    "nextOffset": {
-      "anyOf": [
-        {
-          "maximum": 9007199254740991,
-          "minimum": 0,
-          "type": "integer"
-        },
-        {
-          "type": "null"
-        }
-      ],
-      "description": "Offset to request the next page, or null when there is no next page."
-    }
-  },
-  "required": [
-    "count",
-    "nextOffset"
-  ],
-  "type": "object"
-}

Changed4 schema fields changedApr 19, 2026

changedInput schema / properties / currentMember / description

Previous value: -"Filter to currently serving members. Defaults to false."New value: +"Filter to currently serving members. Omit to include both current and former members."

addedOutput schema / properties / data

Added value: +{
+  "description": "Paginated member or legislation results. Preserves upstream item shapes.",
+  "items": {},
+  "type": "array"
+}

addedOutput schema / properties / member

Added value: +{
+  "additionalProperties": {},
+  "description": "Member profile detail when operation=\"get\".",
+  "propertyNames": {
+    "type": "string"
+  },
+  "type": "object"
+}

addedOutput schema / properties / pagination

Added value: +{
+  "additionalProperties": false,
+  "description": "Pagination metadata for list, sponsored, and cosponsored operations.",
+  "properties": {
+    "count": {
+      "description": "Total number of matching members or bills.",
+      "maximum": 9007199254740991,
+      "minimum": 0,
+      "type": "integer"
+    },
+    "nextOffset": {
+      "anyOf": [
+        {
+          "maximum": 9007199254740991,
+          "minimum": 0,
+          "type": "integer"
+        },
+        {
+          "type": "null"
+        }
+      ],
+      "description": "Offset to request the next page, or null when there is no next page."
+    }
+  },
+  "required": [
+    "count",
+    "nextOffset"
+  ],
+  "type": "object"
+}

First observedMar 28, 2026

TDQS

A4.7/5.0

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 non-trivial operational context: no name search exists, 'currentMember=true' narrows to sitting members while omitting it includes former members, and sponsored/cosponsored return a 'legislative portfolio' rather than a profile. It stops short of noting pagination limits or result ordering.

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?

Four short sentences, front-loaded with the resource and the costliest gotcha ('No name search'), then filtering rules, then operation routing. No filler and no restatement of schema-declared defaults or patterns.

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?

For an 8-parameter multi-operation tool with an output schema supplied, the description covers everything an agent needs before invoking: capability boundary, filter combinations, prerequisite for the id-based operations, and what each operation returns at a high level. Return-value detail is correctly left to the output schema.

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

Parameters4/5

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

Schema coverage is 100%, so baseline would be 3, but the description goes beyond the schema by stating which parameters combine (stateCode alone, congress alone, or stateCode+congress+district together) and by framing bioguideId as the key that unlocks the non-list operations. That combination logic is not expressed anywhere in the input schema, which makes this genuinely additive.

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?

States the resource (congressional members and their legislative activity) and enumerates the four operations it exposes (list/get/sponsored/cosponsored), so an agent knows the full surface. The explicit negative 'No name search' prevents an agent from burning a call on a nonexistent capability and cleanly separates this member tool from the bill/committee/roll-vote siblings.

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

Usage Guidelines5/5

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

Gives concrete routing rules: use 'list' with stateCode (optionally district), congress, or both; use 'get'/'sponsored'/'cosponsored' only once a bioguideId is in hand, per the schema's required-for note. Even names example filter combinations (118th + CA, CA district 12 in the 118th), leaving little to inference.

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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