Preview run cost

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

The readOnlyHint annotation already covers the safety profile, so the description's added value is the disclosure of what is returned: estimated credits, current balance, and pending committed spend. It also notes that timeout_minutes feeds into the estimate. It stops short of stating whether estimates are guaranteed or how stale the balance figure is.

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: purpose and timing first, then return payload, then the one parameter worth calling out. No filler, no repetition of the name or title, and the most decision-relevant clause is front-loaded.

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 compensates by enumerating the three return values. Combined with a complete parameter schema, full annotation coverage of the read-only nature, and the stated pre-run timing, an agent has everything needed 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 description coverage is 100%, so the baseline is 3 per the rubric. The description restates timeout_minutes and its 1-240 range and adds the causal note that it 'affects the run-cost estimate', which is marginally useful, but it adds nothing about num_runs or agent_uuid beyond what the schema already documents.

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 ('Estimates the credit cost of running an agent against a scenario') plus the key temporal qualifier 'before triggering it'. No sibling tool (evaluate_agent, get_run_details, get_usage_summary) performs pre-flight cost estimation, so the agent can distinguish it immediately.

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?

'before triggering it' clearly establishes the pre-flight use context, which is the main decision point for an agent choosing this tool. However, it names no alternative and gives no explicit when-not condition (e.g., that this is read-only and safe to call speculatively), so it falls short of a 5.

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