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

Goes well beyond the annotations by explaining the non-obvious reason for readOnlyHint=false and idempotentHint=false (per-call x402 payment, repeated calls re-charge) and by clarifying that failed calls are never charged. The pricing model, network, and currency are disclosed, which is exactly the context annotations cannot convey.

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 purpose before the payment caveat, and every sentence carries information. The payment explanation is a touch verbose but justified given it is a non-obvious, consequential behavior.

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 two-parameter tool with no output schema, the description fully specifies the output shape via the transformation rules and discloses the cost and safety profile. Nothing an agent needs to call it correctly 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 already 100%, so the baseline is 3, but the description adds real semantic value with transformation examples (é→e, ß→ss) and confirms the separator default. It stops short of enumerating all separator options, leaving the schema to carry that detail.

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 immediately specifies the transformation rules (accents, case, separator). An agent can distinguish this from siblings like case or url_encode without opening the 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?

Gives concrete use contexts ('file names, URLs and IDs'), which is clear enough to trigger correct selection. However it names no alternatives or exclusions, so it doesn't help an agent choose between this and a similar sibling such as url_encode.

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