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

With only destructiveHint=true and a title in annotations, the description adds real value by disclosing the read-modify-write behavior: it fetches the current record and resubmits it with only the caller's changes, which tells the agent that omitted fields are preserved. It stops short of noting auth requirements, concurrency risk, or what is returned.

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 the action, then the behavior that matters most, then the underlying API call. No filler or redundancy.

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 11 parameters, nested objects, no output schema, and thin schema coverage, the description covers the write mechanics adequately but omits everything about how nested/array fields merge and whether the updated customer is returned. It is enough to call the tool, not enough to call it confidently.

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 only 27% across 11 parameters, so the schema does not carry the burden. The description offers no field-level guidance, such as how nested streetAddress or phoneNumbers arrays are treated under the full-customer PUT, leaving the highest-risk semantics undocumented.

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?

It states a specific verb+resource ('Update a customer') and scopes the intent to contact details, which naturally separates it from bookeo_create_customer and bookeo_get_customer. It never names a sibling explicitly, so differentiation relies on the verb alone.

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?

Usage is implied by the verb, but there is no statement of when to use this versus booking-level tools or create_customer, and no prerequisites (valid id, existing customer) are mentioned. The GET-then-PUT note explains mechanics rather than routing.

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