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

Annotations already declare readOnlyHint=true and idempotentHint=true, so the safety profile is covered. The description adds substantial behavioral detail: it explains return fields (recheck_count, suppressed, confidence, blind_spots), gives a concrete example of the relevance floor, and discloses that silence is not a guarantee for certain domains (e.g., aviation-IT). It also specifies error responses for unknown/malformed trip IDs. This goes far beyond the annotations.

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 description is longer than average, but every sentence adds value, including return structure, examples, and edge cases. It is front-loaded with the core purpose, then details. There is no fluff, though a reader might need to absorb a lot; this density is justified by the tool's complexity.

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 no output schema, the description fully carries the burden of explaining returns. It lists all key output fields, provides an illustrative example, explains blind spots, and documents error cases. This is complete enough for an agent to understand the tool's behavior, limitations, and expected outputs without additional context.

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 0%, so the description must compensate. It does: `since` is explained as optionally scoping the recheck window, and trip_id is described as regex-validated with specific error behaviors. While the exact query format for `since` is not given, the description provides meaningful semantics beyond the raw schema types.

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?

The description opens with a specific, action-oriented statement: 'Explain why a watched trip has produced no updates.' It clearly identifies the resource (watched trip) and the action (explain silence), distinguishing it from sibling tools like get_trip_updates_since or watch_trip.

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?

Explicitly states when to use: 'Use this tool when the user asks why they have not heard anything about a watched trip.' While it doesn't explicitly name alternatives or when-not-to-use, the context is clear and the wording differentiates it from tools that fetch updates or manage watchlists.

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