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

Annotations already declare the safe read profile (readOnlyHint, destructiveHint=false), so the bar is lower. The description still adds real behavioral value: webhook delivery, the dependency on a dedicated permission, empty-list semantics, and the notice codes (feature_in_review, reconsent_required) an agent must interpret.

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?

Three dense sentences that lead with what the tool returns before detailing permissions and alternatives. Parentheticals are compact, though the error-code aside adds some reading load.

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 read-only list tool with no output schema, the description supplies the permission gating, the empty-result condition, and the correct next-step sibling. The only real gap is that the three input parameters are left entirely to the schema.

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 only 33% — unread and accountId carry no description in either place — and the description says nothing about any of the three parameters. With low coverage the description is expected to compensate, and it does not.

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 and resource ('Threads posts that mention the connected account') and immediately positions it against a sibling by noting it is the same shape as list_conversations with kind mention. An agent can tell exactly what this returns without opening another schema.

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?

Names the follow-up tool (send_dm) and the diagnostic sibling (list_platforms) explicitly, and explains the permission condition that makes the list empty. It stops short of a full when-to-use/when-not statement, but the routing context is clear.

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