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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds behavior the annotations cannot express: a 0.04 credit charge only when a page is returned, no charge for a missing API key, not_found, or fetch_failed, and the fact that user comments are excluded. It also states the API key requirement with a signup URL.

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?

Purpose and return contents are front-loaded, then exclusions, then cost/auth behavior, which is a sensible ordering. It runs roughly eight sentences and a few clauses (the pricing detail, the API key line) crowd the middle, but each carries decision-relevant information rather than filler.

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?

An output schema exists, yet the description still summarizes the key returned fields (URL, version line, signature, description, first example) and explains failure modes and billing, so an agent can predict both cost and result shape before calling. For a single-purpose lookup tool with three parameters, nothing material 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 coverage is 100%, so the baseline is 3, and most of the description's parameter guidance (symbol examples, source defaulting, version format) restates the schema nearly verbatim. The one genuine addition is the null semantics for version_applies, but that alone does not lift it above 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?

Opens with a specific verb+resource pair: read one current English manual page for a PHP symbol or a WordPress function, hook, or class. It also bounds the scope explicitly (live php.net and developer.wordpress.org, not archived manuals), so an agent knows exactly what domain of answer this tool produces.

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 concrete when-to-use guidance ('Pass the symbol, for example str_contains or wp_insert_post') plus explicit exclusions: it is not an archive of older manuals and does not search Laravel, Symfony, or Markdown docs. The source-selection rule (omit it and a wp_ name uses WordPress) resolves the only ambiguous choice an agent faces.

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