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

With no annotations supplied, the description carries the full burden and does so well: it discloses the auth mechanism (Bearer API key), the exact price (€0.003 per query, answer=true at the same price), indexing side effects on first call, a 7-day cache with instant repeats, and the returned shape (ranked fragments with section and source url). Cost and caching behavior are exactly the traits an agent cannot infer from 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?

Front-loaded with the purpose, then behavior, then a compact parameter glossary — no filler sentences. Slightly dense, with mild redundancy in restating the 'same price' point and a long single-sentence parameter block that could be easier to scan.

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 six-parameter, zero-coverage schema with a mutation-free but metered operation, the description covers purpose, cost, caching, auth, defaults and return content. Since an output schema exists, the return-value detail it adds is a bonus rather than a gap, and nothing an agent needs to invoke it correctly 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 description coverage is 0%, so the description must compensate, and it does: all six parameters are named with meanings, the registry enum values and auto-resolution order, version default, top_k range and default, and the answer flag's effect and pricing. Minor deduction because it doesn't reconcile with the schema, which types top_k and answer as strings rather than integer/boolean, leaving the true argument format ambiguous.

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 ('Answer a question about a package's README and documentation site') and immediately scopes it to package registries, which cleanly separates it from siblings like web_answer, web_search, llms_txt or paper_search. An agent can decide relevance from the first clause alone.

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 use case is implied clearly (ask a question about a library's docs), and caching plus per-query price give useful decision context, but there is no explicit when-to-use/when-not guidance and no named alternative for cases where the package docs aren't the right source (e.g. general web questions).

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