ebay_send_message

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

No annotations are present, so the description must fully disclose behavioral traits. It does not mention permissions, rate limits, latency, or side effects beyond sending a message. The description is too brief for a communication tool.

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?

Two sentences: first states the purpose, second provides critical usage guidance. No redundant information. Every sentence earns its place.

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?

While the schema covers parameter descriptions, the tool has 6 parameters including nested objects (message_media, reference). The description does not mention attachments or the reference object, which are important for full usage. Lacks completeness for a tool with moderate complexity.

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?

The description adds meaning beyond the schema by clarifying the mutual exclusivity of conversation_id and other_party_username, and the purpose of each ('to reply' vs 'to start a new thread'). This helps the agent understand the parameter relationship beyond individual schema descriptions.

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?

Clearly states the verb 'Send a direct message' and the resource 'buyer'. Distinguishes between starting a new thread (other_party_username) and replying (conversation_id), which differentiates it from sibling tools like ebay_reply_to_message and ebay_send_offer_to_interested_buyers.

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?

Explicitly says when to use: for communicating about orders, answering questions, resolving issues, or providing updates. It also specifies the two scenarios (new thread vs reply) and the required parameters for each, but does not mention alternatives like ebay_reply_to_message.

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