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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, so the bar is lower. The description adds useful behavioral context: it is read-only, an unknown run_id fails with agent_run_not_found, and it returns the run's canonical mission-event records. This exceeds what the annotations alone provide, though it does not detail response ordering or field-level behavior.

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?

The description is three concise sentences with no filler. The core purpose is front-loaded, followed by differentiation from siblings and then behavioral/error details, making it easy to scan.

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 two-parameter read-only tool with complete schema coverage and safe annotations, the description covers selection, behavior, error condition, and return intent. No output schema exists, and the description adequately states that the tool returns canonical mission-event records without needing to enumerate response fields.

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 100%, so the schema already documents run_id and limit well. The description adds the contextual note that run_id selects 'one agent run' and mentions the error for an unknown run_id, but it does not add substantial meaning beyond the schema's own parameter descriptions.

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 ('Fetch') and resource ('canonical mission-event records of one agent run'), and clarifies it as 'the typed, indexed projection of its lifecycle used for audit and replay.' It explicitly distinguishes itself from get_agent_run_events and query_agent_run_mission_events, so an agent can select it unambiguously.

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 explicit routing guidance: use get_agent_run_events for the raw append-only stream and query_agent_run_mission_events to search mission events across runs. This clearly states the condition for choosing this tool versus the relevant alternatives.

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