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

Annotations already cover readOnly/openWorld/destructive safety, and the description adds genuinely new behavior: per-call billing via x402 USDC or card key, 25 free calls, failed calls free. That also explains the meaning of idempotentHint=false ('repeats are not free'). It omits nothing critical, though the return shape is only implied.

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 capability is front-loaded in the first sentence with a concrete example right after. The pricing sentence is slightly padded — 'each call is charged, so repeats are not free' restates the earlier 'Price $0.01/call' — costing a bit of tightness.

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?

With only two parameters, full schema coverage, and annotations carrying the safety profile, the description covers what an agent needs to call it. The only gap is that it never states the response is a single slug string, which is easy to infer but not explicit and there is no output schema.

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 baseline is 3, but the description adds real semantics: the separator defaults to '-' and replaces non-alphanumerics, and the example demonstrates the text input's transformation rules. It adds value beyond the schema's terse 'The text' and '- (default) or _'.

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 ('turn any text into a URL-friendly slug') and details the exact transformations: accent folding (é→e, ß→ss), lower-casing, and non-alphanumeric replacement. The worked example (Crème Brûlée & Straße!) makes the output unambiguous and separates it from siblings like url_encode.

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 clear intended uses ('file names, URLs and IDs'), which tells the agent when to reach for it. It stops short of naming alternatives or exclusions — e.g., it never says why to prefer this over url_encode or case — so the routing decision is only partly covered.

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