send_message

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

No annotations are provided, so the description carries the full behavioral burden and does so thoroughly. It discloses that this is a REAL buyer-facing message, requires user confirmation, is subject to Mercado Livre moderation with account suspension risk, forbids contact information, is limited to 350 characters, and returns message id, moderation status, and date.

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 front-loaded with the core action and then layers in critical warnings, prerequisites, and return information. It is somewhat long and repeats the schema's character limit and moderation warning, but every major sentence contributes useful guidance.

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 annotations and no output schema, the description is complete: it covers side effects, moderation rules, user confirmation, prerequisite context lookup, and return values. An agent has enough information to call it safely and correctly.

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%, so the baseline is 3. The description reiterates the text limit and moderation constraint already in the schema, and adds little new syntax or meaning for order_id beyond what is already documented.

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: send a post-sale message to the buyer of a specific order. It distinguishes itself from sibling read tools like get_order_messages by being the send action, and from claim messaging by restricting to post-sale communication tied to an order.

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 clear usage context: only for post-sale communication tied to an order, confirm exact text with the user before sending, and use get_order_messages first for context. It does not explicitly name send_claim_message as the alternative for claim-related messages, but the scoping exclusion is strong.

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