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

Beyond the readOnly/idempotent annotations, it discloses pagination defaults (50/page, max 100, page-numbered), warns that counts/totals are not revenue figures and include drafts and credit notes, and explains the exact-company-name linkage rule. These are non-obvious semantics that materially affect interpretation of results.

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?

Front-loaded with purpose and fields, then caveats and alternatives in a logical order. Slightly dense at six sentences, and 'Read-only' duplicates an annotation, but every sentence carries actionable content.

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 supplies the returned fields, aggregation caveats, pagination limits, and the linkage semantics an agent needs to interpret results correctly, plus sibling disambiguation. Nothing material is missing.

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 100% and already documents page, limit, and case-insensitive search, so much of the description repeats it. What it adds is framing: search keeps company names containing the text, and paging is by page number with the stated page-size bounds — modest but genuine meaning on top of the 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?

Opens with a specific verb and resource plus the exact returned fields, sort order, and per-customer invoice counts. It is clearly distinct from list_recipients and get_customer, which are named 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?

States the concrete use cases (finding a customer id, seeing all clients including never-invoiced ones) and contrasts with two alternatives: list_recipients reads from finalized invoices and has nothing for uninvoiced customers; get_customer gives the full address. Routing is unambiguous.

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