post_message

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

With no annotations present, the description carries the full burden and does reasonably well: it discloses the mail.thread prerequisite, that HTML is rendered as literal text rather than markup, the delivery semantics of each message_type (emailed to followers vs silent internal log), and the return shape ({message_id} or {error}). It does not cover permissions or whether the post is reversible, which keeps it short of a 5.

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 tightly packed sentences, front-loaded with the action and prerequisite, followed by the formatting caveat and the mode distinction. No sentence is redundant and the return shape is appended compactly.

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 4-parameter mutation tool with no annotations and no output schema, the description covers the prerequisite, the input semantics, and the return contract explicitly. Only permission requirements and the exact meaning of model/record_id are left unstated.

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 0%, so the description must compensate and largely does: it explains body formatting behavior, defines both enum values of message_type, and frames model/record_id via 'on a record.' The two identifier parameters are still only implied rather than named, so it falls short of full coverage.

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+resource+scope: 'Post a plain-text message or internal note on a record.' This is clearly distinguishable from the generic create/update siblings, and the parenthetical prerequisite (requires mail.thread) sharpens what kind of record is eligible.

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?

It gives a usable decision rule for the message_type parameter ('comment' sent to followers vs 'note' internal, not emailed), which is genuine usage guidance. However, it never contrasts the tool with sibling write paths such as create or update, so the agent must infer when posting a message is the right call.

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