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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is fully covered. The description adds some value by enumerating the returned fields (emails, phones, billing and service address, notes, tags), which matters because no output schema exists, but it says nothing about error behavior when the 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 two sentences say nearly the same thing: 'every email and phone, billing and service address, notes and tags' is restated verbatim in the second sentence. Half the text is redundant rather than earning its place, though the return-field enumeration is 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?

For a simple single-record read with no nested objects and a fully documented single required parameter, the description covers what is returned, which is the main gap given the absence of an output schema. Only the behavior for a missing or invalid client_id 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?

Schema description coverage is 100%, and the schema itself explains that client_id comes from list_clients. The description adds no meaning about the identifier format or constraints, so the baseline 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?

The description names the resource (a single client) and the verb implicitly, and the phrases 'One client card' and 'Returns one client' make clear it is a singular fetch, contrasting with the sibling list_clients. It does not name that sibling explicitly, so the distinction is implied rather than stated.

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?

Usage is only implied: the singular 'one client' framing signals this is for retrieving a known client rather than enumerating clients, but there is no explicit when-to-use or when-not guidance. Discovery guidance ('From list_clients') lives only in the schema, not the description.

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