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

With no annotations, the description carries the full burden of disclosure. It mentions the API key requirement, the max of 30 URLs, the difference between global and targeted purging, and an example return payload. It does not explicitly state that purging is irreversible, but the term 'purge' is unambiguous for cache operations. This adds substantial behavioral context beyond the bare 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?

The description is compact and well-organized. The main behavior is stated in two sentences, followed by a 'Requires' line, an 'Args' section, and a 'Returns' section. Every sentence adds value, and the return example is given in a code-style block. There is no redundant or extraneous content.

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 tool with two parameters and no output schema, the description provides everything needed: clear input semantics, behaviors for both modes, a constraint (max 30), a prerequisite (API key), and an example return value. It is sufficiently complete for an agent to invoke correctly without additional context.

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?

The schema provides only titles, so the description compensates by explaining both parameters: 'slug: Site identifier' and 'urls: Optional list of specific URLs to purge' with a concrete example. This gives the agent meaningful guidance on input format and purpose, though it could go further by specifying the string format for slug (e.g., a domain or ID).

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 opens with a specific verb and resource: 'Purge Cloudflare CDN cache for a site.' It immediately clarifies the two modes (with and without urls) and the effect of each. This distinguishes it from sibling tools like cache_flush by focusing on Cloudflare and the exact behavior.

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 clearly states when to use each mode: 'Without urls: purges all cached content... With urls: purges only the specified URLs.' It also mentions the requirement for a write-scoped API key. However, it does not explicitly mention alternative tools or when not to use this tool, so it falls slightly short of a 5.

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