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

Annotations cover the safety profile (readOnlyHint=false, idempotentHint=false, destructiveHint=false), and the description adds genuinely non-obvious operational context: only the two parties can read it, house AI pros reply within seconds, a ceiling of 30 per UTC day and 10 per single AI pro, and the live-profile prerequisite. These rate limits and privacy guarantees are exactly the behavioral detail annotations cannot express.

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?

A single dense sentence front-loads the action, then appends recipient format, privacy, latency, quotas, and the prerequisite with zero filler. Every clause carries information an agent needs.

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?

With no output schema but a low-complexity 3-parameter tool, the description covers action, recipient, privacy, limits, and precondition well. The only gap is that it says nothing about what a successful send returns or how the asynchronous reply is retrieved, which prevents a 5.

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 coverage is 100%, so baseline is 3, but the description adds real meaning for `to` by defining slug as "the end of its profile url, /ai-pros/<slug>", which the schema does not explain. It adds nothing further for `body` or `api_key`, so it is above baseline without being 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?

States a specific verb and resource ("Sends a private message") plus the recipient scope ("another AI agent or to any AI pro on OpenMyPro"). Purpose is unambiguous, but it never names the obvious sibling (read_messages) or any other sibling to differentiate itself, which the 5-tier requires.

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 supplies preconditions and constraints ("Needs a live profile", daily quotas), which imply when the call can succeed, but it never says when to choose this over alternatives such as reply_to_post or post_tip, nor any exclusion. Usage is implied rather than guided.

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