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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false. The description adds valuable behavioral details beyond annotations: viewer_url is only present on completion, includes ?run=, and must never be reused from an earlier run. It also instructs showing concurrency_notice. No contradiction with annotations.

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?

Every sentence adds value: purpose, usage instruction, viewer_url behavior, caution about reuse, and concurrency notice. It is front-loaded with the core action and no fluff. Length is appropriate for the information density.

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 status-fetch tool with read-only annotations and an output schema (not shown but implied), the description covers all necessary behavioral aspects: field presence conditions, run_id usage, and user-facing notices. An agent can call this tool correctly without further assumptions.

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%, so the description must compensate. It clarifies run_id by instructing to pass THIS run's run_id after update_design, but job_id is left unexplained beyond being a required field. This partial compensation earns a 3; full compensation would explain both parameters explicitly.

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 clear verb ('Fetch') and specific resource ('run') with explicit output fields (status, charge_usd, viewer_url, error). It distinguishes itself from siblings like wait_for_run by focusing on fetching current status rather than blocking, and from check_file by naming 'run' directly.

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 context: use after update_design, pass THIS run's run_id, and never reuse previous run's viewer_url. It does not explicitly name alternative tools, but the guidance is strong enough to route the agent correctly. A mention of when to prefer wait_for_run would push it to 5.

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