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

Annotations already establish read-only, idempotent, non-destructive, closed-world behavior. The description adds substantial context beyond that: which networks are queried, that X comments are excluded, that commenter suggestions appear on @handle networks, and exactly how to merge item.insert and item.mention into the post payload.

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 purpose is front-loaded and the remaining sentences carry non-obvious integration rules. The description is dense but largely earns its length; minor tightening could improve scanability, but it is appropriately sized for a multi-network lookup tool with no output schema.

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?

Given the tool's network-specific complexity and lack of an output schema, the description supplies the critical usage rules and field names (item.insert, item.mention). It stops short of describing result ordering, pagination, or the full response shape, but it directs the agent to the answer for handle format examples.

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%, so both parameters are already documented in the input schema. The description reinforces how account_id relates to list_accounts and implies query behavior, but it does not add new syntax or semantic detail beyond the schema's own descriptions.

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 opening sentence states the resource and purpose precisely: people and pages to @mention in a post to one account. It distinguishes network-specific behavior, so an agent knows exactly what this tool returns and for which platforms. No sibling tool performs this lookup, so no explicit differentiation is needed.

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 explains when lookup is available and when it is not, including which networks have no lookup and what to do instead (ask the user for the full handle). It also says how to apply the results, but it does not explicitly compare alternatives or state a triggering condition like 'use this while composing a post'.

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