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

Beyond the annotations (which indicate a write operation but not destructive), the description adds that messages are visible to both buyer and worker. This is a key behavioral trait. It does not cover aspects like immediate sending, moderation, or immutability, but the added visibility context is valuable.

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 two sentences, front-loaded with the core action, and includes a second sentence for context. Every sentence earns its place with no unnecessary words.

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 tool has 5 parameters (3 required) and an output schema (not shown), the description covers the purpose, visibility, and typical usage scenarios. It does not explain the output, but that is acceptable since an output schema exists. The description is slightly incomplete about whether messages can be sent after escrow creation, but overall it is sufficient.

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 does not add additional meaning beyond what the schema already provides for parameters like job_id, message, sender_role, etc. It repeats the purpose but not the semantics.

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 clearly states 'Send a message on a job thread' and provides specific use cases: clarifying requirements, sharing progress, or negotiating. This distinguishes it from sibling tools like read_job_messages, which only read messages.

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 explains when to use the tool (for job-related communication) and that it's for communicating within the platform. However, it does not explicitly state when not to use it or compare it to alternatives like email or other messaging tools.

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