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

The annotations already disclose that this is a non-read-only, destructive operation, so the safety profile is covered structurally. The description adds nothing beyond that: it does not say whether completion is reversible, whether it mutates the task's status versus removing it, or which account is affected. With annotations present the bar is lower, but there is no added behavioral context at all.

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 zero padding or wasted words. It is efficient, though its brevity borders on under-specification rather than pure concision.

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 simple two-required-parameter tool with a fully documented schema and annotations, this is the minimum viable definition. It omits the one thing the schema cannot convey — what "completed" actually does to the task and whether it can be undone — which matters given the destructiveHint.

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% — every parameter, including the optional account selector, carries its own description. The tool description contributes no additional meaning about task_id/tasklist_id pairing, so the 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?

"Mark a task as completed" gives a specific verb and resource, so an agent knows exactly what operation this performs. It does not distinguish itself from the sibling gws-mcp__tasks_update, which is the most likely alternative for changing a task's state.

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 guidance on when to reach for this tool rather than tasks_update, nor any stated preconditions (task must exist, must be in the given task list). The agent must infer the choice from sibling names alone.

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