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

Beyond the annotations (write, idempotent, non-destructive, closed-world), the description discloses concrete side effects: addresses stop accepting immediately and the timeline remains readable, which tells the agent data is preserved rather than purged. It does not mention permission requirements or whether the run must still be active.

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, purpose and outcome front-loaded before the behavioral note and usage trigger. Nothing is padded, though the final 'Use when the test is over' sentence is close to restating the obvious.

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?

There is no output schema, and the description covers the core effect on addresses and timeline plus the outcome semantics. It leaves the reason parameter, authorization expectations, and the relationship to rig.run.cancel unexplained, which for a state-changing terminal operation is a meaningful gap.

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 description coverage is only 33%: outcome carries an inline enum description, while reason and run_id are undocumented. The description repeats the outcome values already in the enum but never explains what 'reason' is for or the expected run_id format, so it fails to compensate for the coverage gap.

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 ('End a run') plus the accepted outcomes, so the agent knows it terminates an existing run rather than creating or querying one. It does not, however, differentiate itself from the sibling rig.run.cancel, which is the nearest conceptual alternative.

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?

'Use when the test is over' gives a minimal usage condition, implying this is the normal terminal operation. It offers no when-not guidance and never mentions rig.run.cancel, so the agent must infer the finish-vs-cancel boundary on its own.

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