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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds that values are "as stored in FastBill" and cites the underlying "customer.get" endpoint, but says nothing about pagination behavior or quota consumption beyond what the schema notes.

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 tight sentences that front-load the resource and returned fields, then the filters. The trailing "customer.get" is a minor opaque artifact left over from API documentation but otherwise there is no filler.

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 six-parameter list tool with no output schema, the description compensates by enumerating the returned fields and the filterable dimensions. Pagination and quota details live in the schema, so the remaining gaps are small.

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 83%, so the schema already documents most parameters including term matching, limit defaults, quota cost, and offset semantics. The description restates the filter dimensions (search term, customer number, country, city) without adding format or behavior detail beyond the schema, which is the expected baseline.

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") and enumerates the fields returned, so an agent knows this is a read of customer records. It is clearly distinct from fastbill_get_customer by the 'list' vs 'get' framing, though it never explicitly contrasts itself with sibling 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 filter options imply when the tool is appropriate, but there is no explicit guidance on when to use it versus fastbill_get_customer or the create/update siblings, nor any prerequisites. Usage must be inferred from the filter list.

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