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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds substantial context beyond them: concrete rate limits (100/day anonymous, 1,000/day free key, 50,000/day Agent Pro), the returned fields (slug, endpoint, auth, formats, pricing, 0-100 reliability), and the no-match fallback behavior.

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?

Four dense sentences, front-loaded with the purpose and immediately followed by the return shape and routing rule. The rate-limit sentence is useful for planning but is the least essential clause, keeping it just short of a 5.

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?

For a 4-parameter discovery tool with an output schema and full annotation coverage, nothing needed to invoke it correctly is missing: purpose, fallback semantics, alternative route, and quota constraints are all stated.

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 description coverage is 100%, so need, limit, category and min_reliability are already fully documented, including the enum and list_categories cross-reference. The description adds only indirect meaning (e.g. the reliability score tied to min_reliability) without new syntax or format detail, so the baseline 3 applies.

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?

States a specific verb and resource: 'Map a plain-language goal ... to callable APIs, MCP servers or CLIs.' It also names the sibling it is not (search_registry), so an agent can distinguish it from search_registry/list_entries without opening a schema.

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?

Gives an explicit routing rule: 'For a known keyword or slug, use search_registry.' It also covers the empty-result case by describing coverage='none' plus fallback matches, so the agent knows both when to call it and what it means when nothing fits.

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