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

Annotations already declare readOnly=false, idempotent=true, destructive=true, and openWorld=false, so the safety profile is largely covered. The description does add one real behavioral fact not present in annotations: the tool refuses when the target was never saved. It says nothing about the effects of the destructive state change or repeat-call behavior implied by idempotentHint, so it is only marginally additive.

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?

Three short sentences, front-loaded with the core action. The last two sentences ('Refuses when the work item was not saved' / 'Do not mark unsaved work done') restate the same precondition in negative imperative form, a small redundancy that keeps it out of the top band.

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?

An output schema exists, so return values need not be explained, and the precondition coverage is helpful. But for a three-parameter mutation tool with 0% schema coverage and alias-typed ids, the description omits any parameter or workflow detail (e.g., that save_work_item precedes this call), leaving a notable gap for an agent trying to invoke it correctly.

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?

All three parameters (milestoneSetId, milestoneId, workItemId) carry 0% schema description coverage, and the schema defines two of them via $ref aliases with no format or meaning stated. The description mentions none of them, so an agent gets no help understanding which identifiers are required or how they relate.

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 one saved work item done') with clear scope ('one'), so the agent knows this is a single-item state change rather than a bulk operation. It does not explicitly distinguish itself from nearby siblings like declare_milestone_complete or save_work_item, so it stops short of a 5.

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 gives a when-not condition ('Refuses when the work item was not saved. Do not mark unsaved work done'), which is genuine guidance beyond the schema. However, it never names the alternative action (e.g., save_work_item first) nor states when this tool is preferred over the milestone-level completion tools, leaving the agent to infer the workflow.

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