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

Annotations already declare readOnlyHint=true, so the safety profile is covered; the description adds genuinely new behavior: the matching fields for `query` and the fact that `nif` narrows the result to a single customer. It does not mention pagination beyond the `limit` default or result ordering, which keeps it from 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 short sentences, each carrying distinct information (scope, filters, return shape), with the account scope front-loaded. No filler or restatement of the title.

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?

With no output schema, the description usefully states the return shape ('one line per customer: id, name and NIF'). For a read-only list tool that is close to sufficient; only pagination/limit behavior and the total-vs-truncated result question remain unaddressed.

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 coverage is 67% and the description fills the largest gap: the schema only says 'Search term (optional)', while the description specifies that `query` matches company_name, contact_name, or NIF. `nif` semantics are largely redundant with the schema, and `limit` (default 20, max 100) is never mentioned in the description.

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 ('List customers in the user's contix account') and clarifies the two filtering modes. It never names `get_customer` as the alternative for single-record lookup, so sibling differentiation is only partial.

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 explains the two optional filters (`query` for fuzzy matching, `nif` for an exact single match), which implicitly tells the agent when to use which. It gives no explicit guidance on when to prefer `get_customer` or `create_customer`, and never states that a bare call returns all customers up to `limit`.

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