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

The description discloses that the balance is debited, that results arrive within a few minutes, and that calling again on an already-armed scan returns the same result without charging. This adds valuable context beyond the annotations (readOnlyHint false, idempotentHint true) and fully aligns with them.

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 sentences, each carrying essential information: the action and cost, the human approval requirement, and the idempotency/result retrieval. The capitalized 'SPENDS:' warning is a concise, effective structure.

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?

Covers the key operational context: action, cost, approval, latency, idempotency, and how to retrieve results. However, it does not mention error conditions such as insufficient balance or what the immediate response contains, which would be useful for an agent.

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?

The schema already provides a clear description for competitor_scan_id, including how to find it via list_competitor_scans. The tool description adds no further parameter-specific detail, so the baseline of 3 is appropriate given the high schema coverage.

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 opens with 'Arm a prepared scan' and clearly explains the action: the engine is asked and the prepaid balance is debited. This specific verb+resource+side-effect framing distinguishes it from sibling tools like create_competitor_scan, list_competitor_scans, and get_competitor_scan.

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 explicitly instructs to read the amount to the person and get their go-ahead before calling, and directs users to get_competitor_scan for reading results. It does not explicitly exclude alternatives like create or update, but the context makes the appropriate use case clear.

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