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

The readOnlyHint annotation already establishes the safety profile, so the description's marginal job is to add context. It does: it describes the shape of each returned record (invitees, type, outcome) and maps the operation to the backend endpoint (GET /v1/appointments). No output schema exists, so this return-content hint is genuinely additive, though pagination behavior is only implied via the schema.

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?

Two compact sentences that front-load the resource and its contents, then the filtering options, with no filler. The endpoint reference is terse and appended last rather than interrupting the core guidance.

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 six-parameter, zero-required list tool with no output schema, the description covers the resource, its returned fields, and the valid filter combinations. Remaining gaps (pagination mechanics, default page size) are carried by the schema, so nothing critical is missing.

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 description coverage is 100%, so every parameter (start, end, limit, offset, userId, personId) is already documented in the schema. The description only restates the start+end coupling and the person/user filtering that the schema already explains, so baseline 3 applies.

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+resource ('Calendar appointments') and even summarizes the record contents (invitees, type, outcome), so the agent knows exactly what is returned. It does not explicitly name or contrast against close siblings like fub_list_events or fub_list_calls, which leaves some disambiguation to inference.

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?

Gives concrete usage context: filter by person, by user, or by a start+end window, with the explicit constraint that start and end are 'both required together'. There are no when-not conditions or named alternatives, but the calling contexts are clearly laid out.

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