Congress Member Votes

Roll Call Positions

roll_call_positions

Read-onlyIdempotent

ANSWERS "who voted against roll call 100", "how did Texas Republicans split on roll 250", "how many Democrats voted Yea" -- every member's position on ONE roll call (House: the U.S. House Clerk's roll-call votes; Senate: the Congressional Record) with Yea/Nay/Present/Not Voting tallies by party. Pass party (D/R/I), state or position (yea/nay/present/not_voting) to list matching members; with none of these only the tallies and the roll's question, result and bill are returned. A roll number that does not exist in that session returns a named reason.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "party": "R",
      "session": 1,
      "congress": 119,
      "position": "nay",
      "roll_number": 100
    },
    "name": "roll_call_positions"
  }
}

Input Schema

Name	Required	Description
`party`	No	"D", "R" or "I" to list only that party.
`state`	No	Two-letter state code to list only that state's members.
`chamber`	No	"house" (default) or "senate". The two chambers number their roll calls independently.
`session`	No	1 or 2. Default: the newest held for the default Congress.
`congress`	No	Congress number, e.g. 119. Default: the newest held.
`position`	No	yea, nay, present or not_voting.
`roll_number`	Yes	Roll call number within the session, e.g. 100.

Output Schema

Name	Required	Description	Default
`roll`	No
`found`	No
`source`	No
`chamber`	No
`members`	No
`session`	No
`congress`	No
`data_as_of`	No
`live_topup`	No
`rolls_covered`	No
`members_on_roll`	No
`matching_members`	No
`tallies_by_party`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 25, 2026

TDQS

A4.4/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, non-destructive behavior, so the description focuses on useful extra context: default chamber is House, defaults for session/congress, chamber-specific numbering, and error behavior for nonexistent roll numbers. It does not mention auth or rate limits, but with annotations covering safety this is a solid disclosure.

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

Conciseness4/5

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

The description is front-loaded with concrete questions and is dense but efficient. The quoted example questions take some space, but they earn their place by anchoring the tool's purpose and usage.

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 the output schema exists, the description need not explain return values. It covers scope, default behavior, filtering semantics, chamber sourcing, and error handling for missing roll numbers, leaving nothing an agent needs in order to call it correctly.

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 is 3. The description adds meaning beyond the schema by explaining that party/state/position filters cause member listing, while none of these returns only tallies plus the roll's question, result, and bill.

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 precise verb and resource: retrieving every member's position on ONE roll call, with chamber-specific sources. It explicitly contrasts with member-centric siblings by emphasizing 'every member's position on ONE roll call,' so an agent can distinguish it from member_vote_positions.

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 gives strong usage context through example questions and explains that passing party/state/position lists members while omitting them returns only tallies. It does not explicitly name alternative tools or exclusions, but the 'ONE roll call' framing implicitly separates it from member-level siblings.

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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