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

Annotations declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. The description adds valuable context beyond this: it explicitly states 'Active outbound fetch' and discloses the per-target eTLD+1 throttle and token costs. This transparently communicates that the tool makes real network requests and has rate/cost implications, which is essential behavioral information.

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 dense and information-packed, covering purpose, modules, use cases, rate limits, pricing, and return structure in a few sentences. It is well-front-loaded with the core purpose, though the enumeration of 11 modules and return fields makes it somewhat long. Every sentence contributes value, earning a score above average but not perfect due to 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?

Given the tool's complexity (11 modules, enrichment, multiple return fields), the description is remarkably complete. It explains the scan nature, the enrichment output, usage context, rate limits, quotas, and lists the full return object. An output schema exists, so detailed return field explanation is unnecessary, and the description fills the gaps effectively.

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 input schema covers 100% of the parameter semantics: 'domain' is fully described with format and rejection rules. The description repeats the concept of scanning a live site but adds no new parameter-level details beyond what the schema already provides, so the baseline score of 3 applies.

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 clearly states the tool performs an active website security scan using the ContrastScan C engine with 11 named modules, and produces severity-ranked findings and a letter grade. It explicitly distinguishes itself from sibling tools by naming audit_domain and scan_headers as alternatives for different use cases.

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?

Provides explicit guidance on when to use this tool ('hands-on misconfiguration scan') versus alternatives ('audit_domain for passive recon', 'scan_headers for headers only'). Also includes operational constraints such as rate limits (60 req/min) and quota details (Free/Pro), giving clear context for invocation.

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