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

Annotations already declare readOnly, openWorld, idempotent, and non-destructive behaviors, lowering the burden on the description. The description adds useful context: it uses the official Bills API and explains the high-level behavior of returning matching bills with their progress. It does not contradict annotations and provides some extra detail beyond the schema.

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?

The description is three sentences, each earning its place: it states the action and data source, lists filters and return fields, and summarizes the use case. It is front-loaded with the core purpose and avoids redundancy or fluff.

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?

Given the 8 optional parameters, 100% schema coverage, an output schema, and strong annotations, the description provides sufficient context. It mentions the external API source, the type of search, available filters, and the kinds of results returned. There are no significant gaps that would prevent an agent from using the tool correctly.

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 the baseline is 3. The description restates the filtering categories (session, stage, member, house) and mentions sorting, but these are already fully described in the schema. It does not add meaningful per-parameter semantics beyond what the schema already provides, so the score stays at the baseline.

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 uses a specific verb ('Search') and resource ('legislation before the UK Parliament'), clearly distinguishing it from sibling tools like get_bill or bill_stages. It also states what is returned and the use case ('Answers which Westminster bills concern a subject and how far each has progressed'), making the purpose unambiguous.

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?

The description provides clear context that this is a search/filter tool for bills, with explicit mention of searchable fields and filters. It does not explicitly name alternative tools, but the context strongly implies when to use it (e.g., finding bills by subject) versus fetching a single bill or browsing stages. There are no exclusions or conflicting guidance.

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