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

Annotations already declare destructive=true, idempotent=true, readOnly=false, so the safety profile is covered. The description adds real context beyond them: it discloses that the call 'may mutate canonical state/events,' explains that operationKey enables durable reply recovery, and distinguishes it from authoredIdempotencyKey's manifest contract. It still omits error/return behavior and rate/permission constraints.

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?

Four sentences, front-loaded with the core action, then constraints and idempotency semantics. Dense with domain jargon but every sentence carries information; nothing is padded.

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 an 8-parameter mutation tool with no output schema and only 25% schema coverage, the description covers mutation, idempotency, and the run-owned exclusion but says nothing about the arguments payload, return/reply format, or permission requirements. Adequate but with clear gaps for a tool of this complexity.

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 only 25%, so the description must carry weight. It adds genuine meaning for the two key parameters (operationKey for durable reply recovery vs authoredIdempotencyKey for the manifest idempotency contract) and gestures at 'exact epoch.' But six parameters (projectId, environmentId, instanceId, operationId, arguments, epoch) remain unexplained in both schema and description, leaving a substantial 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?

The description states a specific verb and resource: 'Invoke one authored operation on a manual instance at its exact epoch.' It also scopes it against run-owned instances, distinguishing it from the run-oriented siblings. It doesn't explicitly name the sibling alternatives (e.g. service_control, service_read), 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?

It gives a clear when-not signal ('Run-owned instances reject this operator path') and clarifies that a manual probe is not execution/assessment evidence, which helps route the agent. However it never names a preferred alternative or states positively when this is the right tool, so usage is implied rather than directed.

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