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

Annotations already provide readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false, indicating safe read-only behavior. The description adds behavioral info like 'Concise output, no list' and 'Return the single best LLM', which are consistent with annotations. No contradictions.

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?

Two sentences with no wasted words. The first sentence states the purpose, the second provides usage guidance. Front-loaded with the core action and output format.

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 a single well-described parameter, an output schema, and rich annotations, the description covers all necessary aspects: what the tool does, when to use it, and what to expect (concise output). No gaps.

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%, with the parameter 'purpose' already having a detailed description. The tool description mentions 'for a stated purpose' but does not add significant new meaning beyond the schema. Baseline 3 is appropriate.

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 clearly states the tool returns 'the single best LLM for a stated purpose', with a specific verb and resource. It also distinguishes from siblings by emphasizing 'Concise output, no list' and 'when the user has settled on the criteria and just wants one answer', contrasting with sibling tools like 'rank' or 'compare'.

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 explicitly says 'Use when the user has settled on the criteria and just wants one answer', providing clear context for when to use this tool. However, it does not include explicit exclusions or mention of alternative tools, though sibling names are available for the agent to infer.

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