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

Annotations already declare this as a non-read-only, open-world, non-idempotent, non-destructive operation. The description adds useful behavioral context beyond annotations: the handover is asynchronous, nothing changes until the controlling app acts, and it only works when Conversation Routing is not used. It stops short of describing failure modes or response details beyond 'Returns the chat'.

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 description is compact and mostly front-loaded, but it opens with an awkward sentence fragment ('Facebook, and Instagram connected via Facebook Login') before getting to the action. The remaining sentences are efficient and each carries useful constraint or routing information.

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 complex cross-app handover tool with no output schema, the description supplies the key prerequisites, dependency on the owning app, routing limitation, and sibling relationship. It could say more about what 'Returns the chat' includes or what happens if the request is not fulfilled, but it is largely complete for correct invocation.

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%, and both parameters are already documented in the input schema. The description does not add syntax or meaning beyond the schema, so baseline 3 is appropriate.

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 clearly states the specific action: ask the currently controlling app to hand thread control to Postproxy for Facebook/Instagram chats. It distinguishes this from the sibling `dm_chat_thread_control_take` by calling itself the counterpart, so an agent can select it without opening the 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?

It gives explicit preconditions: the Page must NOT use Conversation Routing, control does not change until the other app acts, and the agent should check ownership with `dm_chat_thread_owner`. It also clearly frames the tool as the counterpart of `dm_chat_thread_control_take`, providing a direct alternative.

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