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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds the identity-scoped lookup behavior, but says nothing about result volume, ordering, or the fact that unmatched identities return an empty page (that detail lives only in the schema).

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?

Very short and front-loaded: the purpose sentence comes immediately. The title text 'Find contacts' is duplicated verbatim at the top, which is minor waste but the rest 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 simple read-only list tool with a rich schema and full annotation coverage, the description covers the core lookup semantics. Pagination and expand behavior are delegated to well-written schema descriptions, and no output schema exists to explain, so remaining gaps are small.

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 83%, so the schema already explains limit, cursor, expand, username and platformId in detail. The description adds only that the identity filter is a platform paired with one of the two identity keys, which is marginal beyond the schema. 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?

States a specific verb (find) and resource (contacts) and narrows the scope to lookup by platform identity, which separates it from contacts_get (by ID) and contacts_update. It does not name a sibling explicitly, so it lands at 4 rather than 5.

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 implies when the tool applies — you have a platform plus a platformId or username — but never states when to prefer it over contacts_get or other lookup paths, nor any prerequisite such as the team needing the platform enabled. Usage is inferable, not spelled out.

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