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

Annotations already declare idempotentHint=true, destructiveHint=false, and readOnlyHint=false, so the safety profile is covered. The description adds that the operation is reversible (setting completed: false), which is useful non-obvious behavior, but it omits anything about permissions or side effects, so it adds only modest value beyond the annotations.

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 waste; the reverse-case clause is compact and relevant. It is efficient, though so terse that it leaves the sibling question unaddressed.

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 annotations covering safety and an output schema present, the main remaining gap is routing: nothing says when to use this rather than update_task or delete_task in a crowded 13-tool family. Adequate for a simple toggle but not fully complete in context.

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 both parameters are fully documented with types and a stated default. The description's parenthetical reinforces the boolean semantics but introduces no format or constraint information the schema lacks; baseline 3 applies.

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 specific verb and resource ('Mark a task as completed') and clarifies the toggle direction. However, it never distinguishes itself from the sibling update_task, which plausibly could also change completion state, so an agent must guess which to pick.

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?

Usage is implied by the parenthetical 'or not completed with completed: false', which tells the agent this covers both directions. There is no explicit when-to-use vs update_task, no prerequisites, and no note about what happens to a completed task's other fields.

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