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

The description adds the behavioral detail that only provided fields change (partial update), which is valuable beyond the idempotentHint annotation. It does not contradict the annotation. While it doesn't discuss error handling or permissions, the partial-update semantics is the most important behavior for an agent to know, so this is well handled.

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 short sentences with no filler. It front-loads the action and the key semantic (only provided fields change). Every word earns its place, making it highly efficient for an agent to parse.

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 7 parameters, no output schema, and moderate schema coverage, the description is too sparse. It omits important context such as how to clear fields (via null, which the schema hints at but the description doesn't), what happens if the task id is not found, or what the return value looks like. It also gives no guidance on when to use this vs. complete_task. For a mutation tool with no output schema, this is insufficient.

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 57% (some parameters have descriptions, others do not). The description does not elaborate on any parameters beyond the general 'fields' mention. It does not compensate for undocumented parameters like title, remark, or owner_name. The schema's own descriptions cover id, project, due_date, and priority, but the description adds no parameter-specific value.

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 the verb 'updates' and the resource 'existing task', and explicitly notes that only provided fields change. This distinguishes it from create_task (creation) and complete_task (completion), though it doesn't name these siblings explicitly. The meaning is unambiguous.

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 implies usage for updating existing tasks (not for creation or completion) and clarifies partial-update semantics. However, it does not explicitly state when to prefer this tool over alternatives, nor does it mention any prerequisites or exclusions. The 'existing task' phrasing gives some context, but no direct guidance on choosing among siblings.

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