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

Annotations only supply destructiveHint=true; the description adds a genuinely non-obvious behavioral trait — that it performs a read-modify-write so unspecified fields survive despite Bookeo's PUT taking the full customer. This meaningfully softens the destructive interpretation. It omits permission/auth requirements and return behavior, keeping it short of a 5.

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 with zero filler: purpose first, then the important merge-semantics caveat, then the underlying API call. Every sentence earns its place and the critical information is front-loaded.

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 an 11-param mutation with no output schema and a low-coverage schema, the description covers the single most important behavioral fact (safe partial update). It could do more on param-level guidance and what the response returns, but the core decision-relevant information is present.

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 low (27%) across 11 params including nested phoneNumbers and streetAddress objects, yet the description names no fields beyond the vague 'contact details'. It does clarify that only supplied changes are applied, which informs partial-update usage of params, but does not compensate for the coverage gap.

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 ('Update a customer's contact details') and the underlying API mapping (GET then PUT /customers/{id}), which immediately distinguishes it from sibling bookeo_create_customer and bookeo_get_customer. An agent can identify the operation without opening any 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 context (modifying an existing customer) but never states when to choose this over bookeo_create_customer or bookeo_update_booking, and gives no prerequisites or exclusions. Usage is inferable from the verb but not explicitly guided.

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