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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, and the description adds substantial operational detail: fallback source behavior, 24-hour caching with performance expectations, per-source timeout limits, circuit-breaker thresholds, and the source field in responses. No contradictions 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?

The description is well-structured and front-loaded with purpose, but it has redundancy: the cache is mentioned twice, the source list is effectively repeated, and read-only/idempotent traits restate annotations. Useful content overall, but trimming duplicates would improve conciseness.

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 primary and fallback sources, deduplication, cache behavior, response source field, timeouts, circuit breaker, and an explicit feedback fallback. An output schema exists for return structure, so nothing material is missing for correct invocation.

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 100% and the schema already documents domain as required and protocol-free. The description repeats the same parameter information without adding new constraints, formats, or edge-case details, so it stays at the baseline.

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?

Description states a specific verb ('Enumerate'), resource ('subdomains for a domain'), and method ('via Certificate Transparency logs'). It also clarifies output as a deduplicated list, which distinguishes it clearly from sibling tools like domain_fetch_dns_records and domain_fetch_reverse_ip.

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 purpose is clear enough that an agent can infer when to use it (whenever subdomains are needed). However, there is no explicit when/when-not guidance or mention of alternatives such as domain_fetch_dns_records or domain_fetch_domain_history, so usage is only implied.

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