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

Beyond the readOnly/idempotent annotations, the description discloses crucial behaviors: status='ok' vs 'unavailable' semantics, that total_snapshots is omitted (not zero) on failure, specific error codes in warnings[], and known heavy domains that time out. 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?

The description is relatively long but well-organized: purpose, usage, rate limits, status details, error handling, returns. Each sentence carries necessary information, though the status/error segment is dense and could be tightened slightly. Not wasteful enough for a 3, but not as minimal as a two-sentence ideal.

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 one-parameter lookup tool, the description is exceptionally complete: it covers the return structure, error states, rate limits, alternative tools, and edge cases like heavy domains and CDX timeouts. The output schema existence plus this description leaves no major gaps.

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 100% coverage for the single domain parameter with examples. The description adds no further parameter syntax or format detail; it only references heavy domains in a behavioral context, so it neither improves nor worsens schema coverage. Baseline 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 first sentence clearly states the tool retrieves Wayback Machine snapshots for a domain, listing specific outputs (first capture, latest, total count, snapshot list). It also explicitly distinguishes from the sibling tool by saying 'for full audit use domain_report'.

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 directly states when to use: 'Use to investigate domain history and age' and gives alternatives: 'for full audit use domain_report.' It also provides rate limits (Free: 30/hr, Pro: 500/hr) and fallback guidance for heavy domains.

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