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

Annotations already declare read-only, idempotent, and non-destructive behavior. The description adds a valuable behavioral guarantee: the returned event and its source set are frozen as of emission and later evidence never mutates it. This is exactly the kind of state semantics an agent needs to trust the result.

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?

One concise sentence front-loads the verb, resource, and lookup key, then adds a compact parenthetical explaining immutability. 'Travel Product B' is minor context but does not bloat the description.

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?

There is no output schema, but the description still conveys what the response contains: the disruption event plus its frozen source set as it stood at emission. For a simple read-by-ID tool, this is complete and gives the agent the critical semantic 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?

The schema has one parameter with 0% description coverage, but the description explicitly ties event_id to selecting which disruption event to fetch. It does not specify where the ID comes from or its format, but for a single simple string parameter this is sufficient.

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 ('fetch'), a specific resource ('one disruption event'), and the lookup key (event_id). It also distinguishes itself from sibling list tools like list_disruption_events by emphasizing singular retrieval and the frozen, span-grounded source set.

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?

Clear context: use this tool when you need a single disruption event identified by event_id, especially when evidence-at-emission semantics matter. It does not explicitly name alternatives or exclusions, but the singular-by-ID framing makes the intended use obvious relative to listing tools.

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