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

Annotations already declare readOnly/idempotent/openWorld, so the safety profile is covered. The description adds genuine behavioral context beyond that: the omitted-session default resolves to the 'verified current session', and for topic=sessions the entire global index is returned when session is omitted — a non-obvious behavior worth disclosing.

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 purpose and followed by the two behavioral rules; little waste. Minor noise from the loose 'bill, division, and caucus' enumeration that doesn't match the enum verbatim.

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?

With an output schema, full annotation coverage, and 100% schema descriptions, the description only needs to carry defaults and special cases — which it does. It stops short of saying whether the returned vocabulary is exhaustive or how often session coverage changes, but nothing critical to invocation is missing.

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 goes slightly beyond it by stating a cross-parameter rule not encoded anywhere in the schema: topic=sessions requires omitting session to get the global index, and it labels the default session as 'verified current'.

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 verb 'List' plus the objects (session coverage, bill/division/caucus vocabulary) make it clear this is a reference/vocabulary lookup rather than a data retrieval tool, which implicitly separates it from the get_/search_ siblings. The phrasing 'bill, division, and caucus vocabulary' only loosely maps to the actual enum values (bill_statuses, vote_results, vote_document_types, parties), so the exact scope needs a schema peek.

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?

'Use source-specific terms when constructing filters' implies this should be consulted before building queries against the search tools, and the topic=sessions rule is stated. However, it never names an alternative tool or says explicitly 'call this before canparl_search_bills', leaving the routing inference to the agent.

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