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

With readOnlyHint/idempotentHint already declaring safety, the description adds real context: the snapshot is dated, the session catalog can lag, document subtypes are distinct from parent type codes, and nextCall must be followed to read all entries. These are staleness and completeness traits the annotations cannot express.

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

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

Three sentences, front-loaded with the topic inventory, then staleness and subtype caveats. Dense but each clause carries a distinct warning; only the topic list is close to restating the enum.

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

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

An output schema exists, so return values need not be described, and the description covers the remaining unknowns an agent needs: snapshot staleness, pagination via nextCall, subtype-vs-parent distinction, and session lag. Little is missing for a read-only reference lookup.

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

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 still adds meaning by glossing the enum topics — 'speech reply filters' for speech_types, 'identifier conventions' for identifiers, and 'source coverage' for coverage — clarifying intent beyond the bare enum labels.

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

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

The description states a specific verb ('look up') and enumerates the reference resources covered (document types, committees, parties, sessions, identifier conventions, coverage). This clearly separates it from the sibling search_/get_ tools, which retrieve documents, members, votes, or speeches, even though no sibling is named explicitly.

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

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

Usage is implied rather than stated: an agent gathers that this is the vocabulary tool to consult before or alongside the search tools. There is no explicit 'use this when / don't use this when' or pointer to a specific alternative, so guidance remains inferential.

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