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

Adds substantial context beyond the annotations: platform restriction, the control-state precondition, the downstream effect on dm_message_send, the fact that the receiving app gets a handover webhook with the metadata note, and where the resulting owner_app_id/expires_at appear. The non-idempotent, non-destructive write profile is consistent with the annotations and elaborated meaningfully.

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?

Front-loads the platform scope and the core action, then layers preconditions and effects. Most sentences earn their place, though the numeric app IDs are duplicated from the schema, which is mild waste.

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 mutation tool with no output schema, the description still explains the return ('Returns the chat; metadata.thread_control holds owner_app_id / expires_at'), the platform limits, the control-state precondition, and the cross-tool effect. An agent has enough to call it correctly and predict the outcome.

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 100%, so all three parameters are already documented, including the target_app_id and metadata semantics. The description restates the app IDs and the platform restriction but adds no syntax or format detail beyond the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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 names a specific verb+resource: handing a conversation to another Meta app via the handover protocol, with the platform scope (Facebook & Instagram only) stated up front. It clearly describes the 'pass' operation. It does not name the sibling tools (dm_chat_thread_control_request/take/release), so an agent must infer the distinction from the verb rather than being routed explicitly.

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?

Gives a concrete precondition: 'Only works while Postproxy controls the conversation or it is idle,' plus the consequence of not having control ('dm_message_send is rejected until control comes back'). It also names the alternative destinations (Page Inbox, Instagram Inbox app IDs). What's missing is an explicit statement of when to choose pass over request/take/release.

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