Send Page Message

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

Annotations already declare readOnlyHint=false, idempotentHint=false, and destructiveHint=false, so the agent knows this is a mutating, non-idempotent, non-destructive operation. The description adds permission requirements and a time-window limitation, which are operational constraints beyond the structured hints. This adds meaningful context without contradicting annotations.

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 well-structured: a one-sentence purpose followed by a bulleted argument list and two constraint lines. Every sentence adds operational value with no redundancy or filler.

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?

The description covers the action, all parameters, the required permission, and the 24-hour messaging window constraint. It lacks return-value or error semantics, but no output schema exists and the primary invocation requirements are fully addressed, making it nearly complete for an agent.

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 only 33% (only recipient_id has a description). The description fills the gap by defining page_id as 'Facebook Page ID', recipient_id as 'PSID (page-scoped user ID)', and message as 'Message text', clarifying the PSID acronym and adding meaning to all parameters.

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 states a specific verb and resource: 'Sends a message from a Facebook Page to a user' and adds the key constraint '(in an existing conversation)'. This clearly distinguishes it from page posting tools like meta_create_post and Instagram messaging tools like meta_send_instagram_message.

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 explicitly states 'Requires pages_messaging permission' and 'Only works within the 24-hour messaging window', giving clear conditions for appropriate use. It does not name alternative tools, but the constraints effectively guide when this tool is viable.

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