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

Annotations already declare destructiveHint=true and idempotentHint=true, so the description is not obligated to restate safety. What it does add is the partial-update contract ("only the fields you provide are changed; omitted fields keep their current value"), which materially reduces the risk of an accidental full overwrite. It never explains what "destructive" means here, e.g. that supplying participantIds replaces the traveler set outright.

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-loaded with what the tool does and immediately followed by the behavioral rule that matters most. No filler and no repetition of the schema.

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 8-parameter destructive mutation with no output schema needs a bit more: the deferred country rules and date-format expectations are left unresolved, and the destructive semantics of replacing participants are not surfaced. The partial-update rule and the guide pointer cover the essentials, but not the full picture.

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 only 25% schema description coverage, the description needs to carry parameter meaning, but it addresses only the omit-to-keep rule generically. Parameters like countryCode (whose rules are merely deferred to log_stay), checkInDate/checkOutDate format, and the max-length constraints on city/name/notes get no explanation here. The one genuinely useful element, participantIds being a complete replacement, lives in the schema rather than the description.

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?

"Update fields on an existing stay by id" gives a specific verb, resource, and targeting key, which cleanly separates it from update_expense, update_journey, and update_loyalty_account as well as from get_stay/delete_stay/log_stay. The scope of the mutation (a subset of stay fields) is stated in the same breath.

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?

It tells the agent to call get_tripledger_guide first when unfamiliar with TripLedger semantics, and that country rules mirror log_stay — both explicit routing cues. It stops short of naming when to use this instead of delete_stay plus log_stay (full replacement) or when not to use it.

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