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

The destructiveHint annotation already flags this as a mutation, and the description reinforces it with 'MUTATES' plus a critical behavioral detail the annotations do not carry: PATCH semantics where only included fields change. It stops short of noting auth requirements, side effects on related records, or idempotency.

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 tight sentences, front-loaded with the mutation warning and endpoint before the parameter guidance. Every sentence carries actionable information with no repetition of schema content.

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?

For a 7-parameter mutation tool with a nested passthrough object and no output schema, the description covers the mutation risk, PATCH semantics, and the role of the `fields` catch-all. It is complete enough to invoke correctly, though it omits confirmation of what a successful response returns.

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 coverage is 100%, so the baseline is 3, but the description adds meaning beyond the schema by explaining that `fields` is a passthrough for arrays and undocumented fields, and that the body is merged with the typed fields. This clarifies how `fields` interacts with the typed properties rather than merely restating them.

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 and resource ('updates an existing guest') and anchors it to the underlying API operation PATCH /v2/guests/{id}, which distinguishes it from the sibling create_guest and update_booking. An agent can identify the tool without opening the schema.

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 directs the agent to use the `fields` passthrough for arrays (email_addresses/phones/addresses) and other documented fields, which is clear routing guidance. It lacks any when-not-to-use or prerequisite guidance (e.g., required permissions), so it falls short of a 5.

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