Send a private message

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

Annotations already signal a non-read-only side effect (readOnlyHint=false, openWorldHint=true), but the description adds valuable context: messages go out under the user's brand, require user approval, and have platform-specific delivery windows. This goes beyond the structured annotations without contradicting them.

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 sentences, each earning its place: the purpose, the two failure-prone rules, and the approval/brand requirement. It is front-loaded and contains no redundancy.

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 output schema exists and annotations cover the side-effect profile, the description sufficiently covers the key failure modes and approval workflow. It could be more explicit about the roles of id_account and id_contact, but the overall picture is complete enough 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 60%, and the description compensates by explaining when template_name is needed and that the text must be user-approved. It does not clarify id_account or id_contact, but those are inferable from the tool name and context, so the added meaning is meaningful but not exhaustive.

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 opens with a specific verb and resource: 'Send a private message to a contact.' This clearly distinguishes the tool from sibling tools like list_messages or reply_to_comment, and the platform-specific rules add further precision about what it does.

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 provides actionable timing rules: free-form messages only work within a 24-hour window on Facebook, Instagram, and WhatsApp, and outside that window WhatsApp requires template_name. This is strong 'when to use' guidance, though it does not explicitly name alternatives or state when to prefer a different tool.

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