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

The description discloses substantial behavior beyond the sparse annotations: re-adding the same name updates stored address, email, and VAT id, while an identical record is refused with the existing record's id. This gives the agent a precise mental model of the upsert and duplicate-handling behavior.

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?

Two tightly written sentences with the primary purpose first and the behavioral edge cases second. Every clause contributes new information, with no filler or repetition of the title or schema.

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?

The definition covers purpose, usage, update semantics, and duplicate-conflict response, which is substantial for a tool with no output schema and sparse annotations. The agent has enough information to invoke it correctly and anticipate key edge cases.

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?

With only 25% schema description coverage, the description compensates by explaining that name is the identity key and address/email/vat_id are the updateable fields. It does not provide format or validation details, but it adds meaningful semantic context beyond the raw schema.

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?

The description opens with 'Store a client', a specific verb and resource, and immediately adds the purpose: so invoice_create can refer to them by name. This clearly distinguishes client_add from read-only siblings like client_list or invoice tools.

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 provides clear context by tying the tool to invoice creation and explaining that re-adding the same name updates an existing client. It does not explicitly name alternatives or state when not to use it, so it falls short of full exclusion guidance.

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