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

Annotations already declare readOnlyHint, openWorldHint and idempotentHint=false. The description goes beyond them usefully: it discloses the retrieval strategy (project llms.txt, docs pages, or latest release README fallback), the token-budget constraint, that sources and the current version are returned, and the payment model ($0.005 USDC via x402 or prepaid credits, free trial). That is genuine added context for a paid, open-world call.

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 core is front-loaded, but the description is padded: 'Stop your assistant using stale APIs' and 'Stops agents using stale APIs' say the same thing, the ecosystem list appears twice, and '★ One of our best tools' is promotional filler that does not help invocation.

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 read-only fetch tool with a full schema and an output schema, the description covers what it returns, how it sources content, the version freshness, and the cost/payment path. An agent has enough to decide and call it correctly; only sibling routing is thin.

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 all four parameters (library, ecosystem, topic, tokens) are already documented with examples, enums, defaults and bounds. The description restates the ecosystems and the topic-trimming and token-budget concepts but adds no syntax or format detail beyond the schema, so the baseline of 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 concrete verb and resource (fetch latest docs for a named library) and scopes it across npm, PyPI, crates and Go, plus the topic-trimming behavior. It does not, however, distinguish itself from plausible siblings like docs-find, docs-answer, or library-research, which an agent could easily confuse it with.

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 opening and closing lines imply the use case ('stop your assistant using stale APIs'), which gives an agent a reason to call it. But there is no explicit when-not guidance and no named alternative (docs-find, docs-answer, library-research) to route between, so the selection logic is left to inference.

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