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

Annotations already declare readOnlyHint=true and destructiveHint=false, so safety is covered. The description adds genuinely new behavioral context beyond that: the expected runtime ('runs normally take several minutes') and the meaning of the 'partial' failureReason, which is not derivable from structured fields.

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 tight sentences that front-load what the tool returns, then the runtime expectation, then the routing hint. Slightly dense with parenthetical caveats, but no filler.

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 the description is not obligated to explain return values, yet it still disambiguates the failureReason semantics and runtime. Combined with annotations covering the safety profile, an agent has enough to call this 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?

Schema coverage is 0%, but there is only a single required parameter, testId, whose name and type make its meaning self-evident. The description does not restate the parameter or clarify its format, so it neither compensates for nor worsens the coverage gap – baseline 3 is appropriate.

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 ('returns a one-off progress snapshot for a running usability test') and enumerates the payload fields (phase, percent complete, failureReason). It implicitly distinguishes itself from the sibling wait_for_results by being the one-off rather than the follow-to-completion tool.

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?

Explicitly names the alternative and the condition selecting it: 'wait_for_results is the usual way to follow a test to completion,' which tells the agent this tool is for a single snapshot rather than polling. It stops short of stating when this tool is preferred or what to do if the test has already finished.

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