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

Annotations already declare readOnlyHint=false, idempotentHint=true and destructiveHint=false, so the safety profile is covered. The description usefully adds the concrete field-level effect (sets status='done' and completed_at), but says nothing about error cases such as an unknown task_id or a task already completed.

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 behavioral summary is front-loaded in the first sentence, and the Args block is terse and each line earns its place. No filler, though the docstring-style layout is slightly verbose for three parameters.

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 small mutation with no output schema, the description covers the target, the side effects and all parameter semantics, and idempotency is supplied by annotations. Only failure-mode behavior (unknown or already-completed task) is unaddressed.

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 carry the load, and it does: task_id is documented as a UUID, result as an optional note, and completed_at as an optional ISO-8601 override defaulting to now. That maps cleanly to all three parameters and supplies the format detail the schema lacks.

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 ('Mark a standalone task as done') and explicitly names the state change it performs (status='done', completed_at). The word 'standalone' hints at the distinction from complete_agent_task, but the sibling is never named, so the differentiation is implicit rather than explicit.

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?

There is no explicit when-to-use/when-not guidance and no named alternative, even though complete_agent_task sits right alongside this tool in the sibling list. The qualifier 'standalone task' implies scope but leaves the agent to infer that agent tasks are handled elsewhere.

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