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

Annotations already establish this is a non-read-only, non-destructive, closed-world write, so the description only needs to add context — and it does, by disclosing the permission constraint (only the creator or assigned agent may post) and by stating the post does not mutate task status. It stops short of saying whether decline has any downstream effect, whether messages are visible to all parties, or whether there are rate limits.

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 front-loaded sentence with no filler; the actor constraint comes first and the side-effect boundary second. It is compressed to the point that a little more detail on the type/data fields would have been worth the extra words, but nothing present is wasted.

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 5-parameter write tool with one undocumented nested object and no output schema, the description covers roles and side-effect scope but leaves the payload shape and the return contract unaddressed. An agent can call it correctly for a plain message but would be guessing on 'data' and on what the response confirms.

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?

With 60% schema coverage the baseline is 3: task_id, body length limit, and idempotency_key are fully documented in the schema, so the description need not repeat them. However it merely echoes the enum values without explaining when 'progress' versus 'decline' should be chosen, and the nested 'data' object — the one parameter documented nowhere — receives no mention at all.

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 states a concrete verb (post) and the three payload kinds it accepts (message, progress update, decline) on a task, and the parenthetical '(no status change)' carves it away from siblings like apply_task, start_task, and cancel_task. It is specific enough to identify the operation, though the resource is only implied by the tool name rather than stated in the text.

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 caller precondition ('Creator or assigned agent') and one negative cue ('no status change'), which implicitly routes status-changing work to apply_task/start_task. It never explicitly says when to use each of the three types, when decline is preferable to cancel_task, or what to do if neither role applies — so the guidance is implied rather than stated.

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