congressgov-mcp-server

Congress.gov Roll Votes

congressgov_roll_votes

Read-onlyIdempotent

Retrieve U.S. congressional roll call votes and individual member voting positions for either chamber. Set 'chamber' to 'house' (default, from the Congress.gov API) or 'senate' (from the Senate's official LIS feed). Use 'list' to find votes by congress and session (newest first by default), 'get' for vote details (question, result, tallies, party breakdown, associated bill/nomination/amendment), or 'members' for how each member voted.

Input Schema

Name	Required	Description	Default
`limit`	No	Results per page (1-250).
`order`	No	Sort order for 'list'. 'recent' (default) returns newest first; 'oldest' returns ascending. House sorts by vote update date (with 'recent', offset=0 always returns the strictly newest page); Senate sorts by roll call number. Ignored by 'get' and 'members'.	recent
`offset`	No	Pagination offset.
`chamber`	No	Chamber whose votes to query. 'house' (default) draws from the Congress.gov API; 'senate' draws from the Senate's official LIS roll-call feed. Roll call numbers reset each session and are specific to one chamber.	house
`session`	Yes	Session number (1 or 2). A congress's first year is session 1 and its second year session 2; a second session can run into January 1–3 of the following year (the 116th Congress's second session voted on 2021-01-01).
`congress`	Yes	Congress number.
`operation`	Yes	Which data to retrieve.
`voteNumber`	No	Roll call vote number. Required for 'get' and 'members'.

Output Schema

Name	Required	Description
`data`	No	Result rows. Per-tool item shape is rendered in the markdown body.
`vote`	No	Dynamic upstream JSON record.
`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.

Changed3 schema fields changedNov 2, 2026

changedInput schema / properties / session / description

Previous value: -"Session number (1 or 2). Odd years are session 1, even years session 2."New value: +"Session number (1 or 2). A congress's first year is session 1 and its second year session 2; a second session can run into January 1–3 of the following year (the 116th Congress's second session voted on 2021-01-01)."

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. `incompatible_identity`: A list operation carries an entity identifier that only a detail operation uses. 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. `incompatible_identity`: A list operation carries an entity identifier that only a detail operation uses. 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",
-  "incompatible_identity"
-]New value: +[
+  "not_found",
+  "rate_limited",
+  "invalid_request",
+  "api_key_rejected",
+  "upstream_error",
+  "upstream_timeout",
+  "incompatible_identity"
+]

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. `incompatible_identity`: A list operation carries an entity identifier that only a detail operation uses. 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",
+  "incompatible_identity"
+]

Changed1 schema field changedAug 30, 2026

addedOutput schema / properties / vote

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"
-]

Changed2 schema fields changedJun 2, 2026

addedInput schema / properties / chamber

Added value: +{
+  "default": "house",
+  "description": "Chamber whose votes to query. 'house' (default) draws from the Congress.gov API; 'senate' draws from the Senate's official LIS roll-call feed. Roll call numbers reset each session and are specific to one chamber.",
+  "enum": [
+    "house",
+    "senate"
+  ],
+  "type": "string"
+}

changedInput schema / properties / order / description

Previous value: -"Sort order for 'list', by vote update date. 'recent' (default) returns newest first; 'oldest' returns ascending. With 'recent', offset=0 always returns the strictly newest page. Ignored by 'get' and 'members'."New value: +"Sort order for 'list'. 'recent' (default) returns newest first; 'oldest' returns ascending. House sorts by vote update date (with 'recent', offset=0 always returns the strictly newest page); Senate sorts by roll call number. Ignored by 'get' and 'members'."

Changed6 schema fields changedMay 30, 2026

removedOutput schema / description

Removed value: -"Detail-mode key 'vote' carries: Vote record for `get` and `members` (question, result, party totals, member positions); absent for `list`."

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"
+]

Changed5 schema fields changedMay 21, 2026

changedInput schema / properties / order / description

Previous value: -"Sort order for 'list' (sorts by update date). 'recent' (default) is newest first; 'oldest' is ascending. The upstream API ignores sort params on this endpoint, so 'recent' is implemented client-side by fetching the tail and reversing. Ignored by 'get' and 'members'."New value: +"Sort order for 'list', by vote update date. 'recent' (default) returns newest first; 'oldest' returns ascending. With 'recent', offset=0 always returns the strictly newest page. Ignored by 'get' and 'members'."

changedOutput schema / description

Previous value: -"Vote data from Congress.gov API."New value: +"Detail-mode key 'vote' carries: Vote record for `get` and `members` (question, result, party totals, member positions); absent for `list`."

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 21, 2026

addedInput schema / properties / order

Added value: +{
+  "default": "recent",
+  "description": "Sort order for 'list' (sorts by update date). 'recent' (default) is newest first; 'oldest' is ascending. The upstream API ignores sort params on this endpoint, so 'recent' is implemented client-side by fetching the tail and reversing. Ignored by 'get' and 'members'.",
+  "enum": [
+    "recent",
+    "oldest"
+  ],
+  "type": "string"
+}

First observedMar 28, 2026

TDQS

A4.5/5.0

Behavior4/5

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

Annotations declare readOnly/idempotent/openWorld, so safety is covered. The description adds genuine behavioral context beyond that: the two chambers come from different data feeds (Congress.gov API vs Senate LIS), and default newest-first ordering differs by chamber. It doesn't detail return shape, but an output schema exists.

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 sentences, front-loaded with the core purpose, then chamber source, then operation routing. No filler; each clause carries actionable detail.

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?

Given a complete schema, existing output schema, and safety annotations, the description covers purpose, chamber data provenance, and operation routing. Nothing essential for correct invocation is missing.

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 3 applies, but the description adds meaning: chamber selects the upstream data source and operations map to distinct retrieval modes ('list'/'get'/'members'). It reinforces the chamber and operation semantics beyond the schema's enum text.

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 a specific verb+resource ('Retrieve ... roll call votes and individual member voting positions') and covers both chambers. No sibling tool in the list covers roll-call votes, and the description makes that scope obvious.

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?

Explicitly explains which operation to use for what: 'list' to find votes by congress/session, 'get' for details, 'members' for per-member positions, plus chamber selection guidance. It doesn't name alternative tools or exclusions, but there is no overlapping sibling, so the guidance is clear in context.

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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