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

With destructiveHint=true already declared, the description still adds real value: it flags this as a WRITE, explains the default trailing-slash cascade behavior, the wildcard support, and that the CDN refetches from origin. It omits auth requirements, rate limits, and whether the purge is reversible, so it is good but not exhaustive.

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-loads the 'WRITE.' marker, then the scope, then the URL-form rules — all tight with no wasted clauses. The trailing 'bunny.net: POST /purge' endpoint note is the one line that does not help an agent decide or invoke, 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?

No output schema exists, so the description carries the return-value burden; it does not say what a purge response looks like or how async results are surfaced. For a one-URL purge mutation the operational semantics (cascade, wildcard, origin refetch) are otherwise well covered.

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, but the description goes past the schema by explaining the default behavior of a trailing-slash URL ('purges everything under it') and how exact_path and wildcards interact. Only the async parameter gets no additional description beyond the schema text.

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 with precise scope: 'Purge one URL from the CDN cache.' The 'one URL' scope implicitly separates it from the sibling bunny_purge_pull_zone_cache, which operates at zone level, so an agent can route between them without opening either 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?

It explains the semantics of the argument (trailing slash, wildcard, exact_path) but never says when to choose this tool over bunny_purge_pull_zone_cache or when a whole-zone purge is preferable. Usage is implied by the tool's scope rather than stated.

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