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

Annotations declare readOnlyHint=false, idempotentHint=true and destructiveHint=true; the description adds genuinely useful context beyond them by clarifying partial-patch semantics ('only the fields you pass are changed; everything else stays') and that no notification is dispatched ('Nothing is sent to the client'). It does not reconcile why a partial, idempotent field update carries destructiveHint=true, which would have been worth addressing.

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 the WRITE mode marker front-loaded, then the mutation semantics, then the prerequisite. 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 19-parameter mutation tool with full schema coverage, existing annotations, and no output schema, the description covers mode, patch behavior, prerequisite, and external side effects. Remaining gaps (error behavior on unknown id, idempotency implications) are minor.

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% across all 19 parameters, so the schema already carries per-field meaning and the baseline is 3. The description only adds the general rule that unspecified fields are preserved — useful but not field-level detail.

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 ('change fields of an existing client') and a distinguishing scope constraint (partial update; only passed fields change). An agent can separate it from billomat_create_client and billomat_get_client 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?

Explicitly prescribes a prerequisite workflow ('Read the client first with billomat_get_client'), which routes the agent to the correct sibling before invoking this one. It stops short of when-not-to-use guidance or alternative update paths, but the operative context is clear.

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