Cancel a 99 ride (gated)

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

Annotations already declare destructiveHint=true and readOnlyHint=false. The description adds useful non-obvious behavior: fail-closed operation, environment-variable gating, and a guest-token limitation. It doesn't contradict the annotations, though the 'cannot charge' phrasing is ambiguous.

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?

Three short sentences front-load the critical fail-closed and permission requirements. The opening sentence earns its place, and the guest-token clause adds context even if somewhat cryptic.

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?

It covers the essential gate conditions and makes the destructive intent clear, but there is no output schema and no description of success/failure return behavior or what response_format changes. Edge-case behavior and return semantics are under-specified.

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 description coverage is only 33%, with ride_id and response_format undocumented. The description mentions explicit_user_intent in prose but does not clarify that it must be set to true or explain the other two parameters. It does not compensate for the low schema coverage.

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?

Name and title clearly specify 'cancel a 99 ride' as a distinct operation from siblings like request_ride and track_ride. The description adds gating context rather than restating the purpose. It lacks an explicit sibling differentiation, so it doesn't reach 5.

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 explicitly lists required preconditions: NINENINE_ALLOW_MUTATIONS, explicit_user_intent, and notes guest tokens cannot charge. This gives clear activation context. It does not state when not to use it or mention alternative tools, so it stays at 4.

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