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

Annotations already declare destructiveHint=true, idempotentHint=true, and readOnlyHint=false, so the safety profile is covered structurally. The description adds real value on top: it enumerates the only two mutable fields, states the URL is immutable, and prescribes the alternative workflow. It does not explain whether omitted fields are preserved or cleared, which would be the remaining useful detail.

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?

Two sentences, no filler, and the mutable-field scope is front-loaded before the URL caveat. Every clause carries information an agent needs.

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 so return values need no explanation, and the annotations carry the safety profile. For a mutation tool with a nested authentication object, the description covers field scope and the URL constraint well, but leaves the credential payload structure unaddressed.

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 50% and the two undocumented parameters are exactly the ones the description clarifies in domain language: 'draft.abandoned opt-in' maps to includeAbandoned and 'outbound credential' maps to the authentication object. This meaningfully compensates for the coverage gap, though it never describes the credential object's internal shape.

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?

Names a specific verb ('Change') and resource ('webhook'), then narrows scope to exactly two mutable fields: the draft.abandoned opt-in and the outbound credential. It also distinguishes itself from the add/remove siblings by stating the URL is immutable and pointing to the remove-and-re-add workflow.

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 an explicit when-not condition (the URL cannot be changed) and names the alternative path (remove and re-add, i.e. fillo_remove_webhook + fillo_add_webhook). However, it never frames the general case for choosing this tool over fillo_add_webhook or fillo_list_webhooks, so the guidance is conditional rather than complete.

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