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

The annotation already covers the read-only, non-destructive, open-world safety profile, so the description only needs to add context — and it does, disclosing the auth requirement ('Cotlet API key with access to this app') and the shape of the returned card. It does not mention rate limits, pagination, or behavior when the client_id is unknown.

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?

The field inventory is stated twice in near-identical form ('contact details, tags, notes, client details, appointments, invoices and message history' vs 'contact details, tags, internal notes, appointments, invoices and the message history'). That duplication costs space without adding information, though the tool's purpose and trigger are front-loaded.

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, describing the returned card fields is genuinely necessary and is done here, and the auth prerequisite is disclosed. For a one-parameter read tool whose safety profile is already in annotations, this is close to complete; only error/absence behavior is 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?

With a single parameter at 100% schema description coverage, the schema already documents client_id and its provenance (from list_clients). The description adds no format, validation, or ID-sourcing detail beyond that, so the baseline of 3 applies.

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 (get one client card) and enumerates the payload it contains. It is distinguishable from thryv_list_clients by the explicit 'Returns one client card' phrasing, though it never names that sibling to sharpen the contrast.

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?

'Use it before replying or invoicing so your agent sees everything about the client' gives a concrete trigger condition for calling it. There is no explicit when-not guidance or named alternative (e.g. list_clients for browsing), so it stops short of a 5.

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