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

No annotations are present, so the description must carry the behavioral burden. 'Fetch' unambiguously signals a read-only, side-effect-free operation, and the list of included data categories sets expectations for the response. It does not mention error/not-found behavior, but for a simple getter this is a minor omission.

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?

A single sentence with no filler. It front-loads the core operation ('Fetch a single contact by id') before enumerating return contents, so every part earns its place.

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 one-parameter getter with no output schema and no annotations, the description is largely complete: it names the input and the main output categories. It could be more explicit about response shape or not-found conditions, but nothing an agent needs to invoke it correctly 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% (id is described as 'Contact UUID'), so the baseline is 3. The description adds no parameter-level detail beyond saying 'by id,' which is already implied by 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?

States a specific verb ('Fetch') and resource ('a single contact by id'), and enumerates returned data categories (tags, addresses, custom fields, recent activity). This clearly differentiates it from list/update/delete sibling tools even without naming them.

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 establishes the obvious usage context: use this when you have a contact id and need one contact's full details. It does not explicitly name contacts_list or state when not to use it, but the 'single contact by id' phrasing is clear enough for selection.

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