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

The description clearly explains the REPLACE semantics and the silent deletion of unspecified legs, which is crucial behavioral information beyond the schema. However, no annotations are provided, so the description carries full burden. It does not discuss required permissions, rate limits, or what happens to other blocks not sent.

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 concise with two clear sentences. It front-loads the purpose and then provides essential behavior. While it effectively earns its place, it could be slightly more structured (e.g., bullet points) for readability, but it remains very efficient.

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?

Given the high schema coverage (88%) and the complexity of the nested objects, the description is appropriately minimal. It does not need to explain return values since there is no output schema. It could mention that authentication requires a bearer token (already noted), but overall it is complete for an experienced user.

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?

With 88% schema description coverage, the schema already describes the parameters well, so baseline is 3. The description adds value by clarifying the REPLACE semantics for legs and the optionality of blocks, which is not captured in the schema. It effectively elevates the understanding beyond the raw parameter names and 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 clearly states it writes 'the planning layer above an itinerary's day-by-day' and distinguishes itself from sister tools like write_itinerary_day_detail. However, it could more explicitly differentiate from update_itinerary or create_itinerary, which also modify itineraries.

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 provides clear usage guidance: it replaces entire blocks, advises to send only intended blocks, and explicitly warns about partial leg lists deleting others. However, it does not specify when NOT to use this tool (e.g., for day-level changes vs. dossier-level changes) beyond the context of the itinerary.

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