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

Annotations only supply destructiveHint=true, but the description adds genuinely useful semantics: omitted fields are preserved, and passing 'contacts' destroys and replaces the existing contact list. That destructive sub-behavior is exactly the kind of context an agent needs to avoid accidental data loss. It stops short of covering permissions, error behavior, or response shape.

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 clauses lead with the action and the partial-update rule before the destructive contacts caveat and the raw endpoint. No filler, well 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 a 15-parameter mutation with no output schema and low schema coverage, the definition covers the update semantics and the destructive contacts edge case but leaves the majority of fields and all failure/response behavior unaddressed. Adequate but with clear gaps.

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 33%, so most of the 15 parameters are undocumented in both places. The description partially compensates by explaining that unpassed fields stay unchanged and that 'contacts' is a full replacement, but it leaves city, phone, state, website, addresses, vat_number, notes, and others without added meaning.

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 client's details') and immediately scopes the operation as a partial update. It is readily distinguishable from the sibling create_client, get_client, and list_clients by verb alone, though it never names those alternatives explicitly.

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?

Use is implied by the verb and the 'only the fields you pass change' clause, which tells the agent this is a patch-style update rather than a full overwrite. There is no guidance on when to prefer this over create_client, when get_client should precede it, or any prerequisite/exclusion.

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