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

Annotations already cover read-only, idempotent, non-destructive, closed-world semantics, so the burden is lighter. The description adds genuinely useful context the annotations lack: the return value is self-contained HTML (implying embeddable, no external asset fetching needed). It does not mention size, caching, or rendering caveats.

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 with no filler. The usage condition leads, which is reasonable, though leading with the action (what it renders) before the when-condition would front-load purpose more effectively.

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 single-parameter read tool with full annotations and an output schema, the description covers what an agent needs: when to use it and what form the output takes. Only minor gaps remain (no note on how large the HTML is or what happens with a missing contact).

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?

There is a single required parameter with 100% schema description coverage ('Contact API id.'). The description adds no additional meaning about contact_id - no mention of format, source, or error behavior for unknown ids - 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 states the resource (a polished profile card for a person) and the output format (self-contained HTML), so an agent understands this renders a contact card rather than returning raw contact data. It stops short of a crisp verb+resource phrasing like 'Render a profile card for a contact', leaving the connection to contact_id implicit.

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?

It gives a clear selection condition: use this when presenting a person to a human in a visual format instead of plain text. That implicitly contrasts with contacts.get, but it never names the alternative tool or states when not to use it (e.g., programmatic consumption), so it falls short of explicit routing.

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