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

Annotations already declare it is a non-destructive write with open-world reach, so the bar is lower. The description nonetheless adds real behavioral detail beyond the annotations: Thryv emails the client a booking confirmation (plus any extra recipients), end time defaults to service length, staff defaults to the primary admin, and per-call user confirmation is required.

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 opening is front-loaded and useful, but the confirmation-email fact is stated twice ('Thryv emails the client a booking confirmation' appears verbatim in sentences 2 and 4), and the phrasing 'Reaches other people: confirm with the user before each call' is clipped and partly redundant with the preceding confirmation sentence.

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 mutation tool with annotations and no output schema, the description covers the key concerns: external side effects (outbound email), defaulted fields, and the API-key requirement. Only minor gaps remain, such as how price_type/price interact and what happens if required lookups (client_id, service) are 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 the schema already documents all 8 parameters, including the end-time and staff defaults. The description largely restates those defaults rather than adding new semantics such as date format constraints or how price_type interacts with price, so the 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: 'Books an appointment on your calendar for a client.' This clearly separates it from siblings like thryv_list_appointments or thryv_mark_no_show, and adds the immediate consequence (client confirmation email).

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 conveys prerequisites (Cotlet API key, user confirmation before each call) and that confirmation can be toggled off for this tool, which is useful context. However, it never names alternatives or states when-not to use this versus siblings such as thryv_create_estimate or thryv_mark_no_show, so usage routing remains implied.

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