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

Annotations already declare readOnlyHint=true, so safety is covered. The description goes beyond that by disclosing what the payload contains, notably that every booking the guest has made is included, which is non-obvious and useful for deciding whether this single call can replace multiple lookups.

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 front-loaded sentence carrying the verb, the identifier, the payload scope, and the underlying endpoint. No filler and nothing important is buried.

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?

No output schema exists, and the description compensates by naming the payload contents, which is what an agent most needs for a single-param read. It omits error behavior for an unknown guestId, a minor gap for a tool of this complexity.

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% and the parameter is self-documented as 'The guest id', so the baseline is 3. The parenthetical '(the guestId on a reservation)' adds real disambiguation by tying the identifier to its source object, distinguishing it from a user or apartment id elsewhere in the API.

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 ('Fetch one guest by id') plus the exact scope of the returned payload (contact details, notes, every booking). The singular 'one guest by id' cleanly separates it from the sibling smoobu_list_guests without opening either 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?

The description implies the usage condition by saying it fetches by 'the guestId on a reservation', so an agent knows it needs an id in hand. However, it never explicitly says when to prefer this over smoobu_list_guests or what to do when the id is unknown, leaving routing to inference.

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