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

With no annotations, the description carries the full burden. It usefully discloses determinism and a per-call cost/auth model (x402 price $0.01/call, USDC, eip155:8453), which is real context. But it omits what happens on an invalid expression, whether validation failure is an error or a field in the response, and any rate-limit or output-shape detail.

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?

Front-loaded with the core capability and kept short. The third sentence ('Use this when...') largely repeats the first, and the pricing sentence is a tacked-on operational detail, but nothing is bloated.

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?

With no output schema, the description does name the three return concepts (plain-English explanation, validation, next execution times), so an agent can anticipate results. The main gap is that it never resolves its overlap with dev_cron_next_runs, leaving routing ambiguous.

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% and both parameters (expr, ref) are documented in-schema, so the baseline is 3. The description's cron format note ('5 fields: minute hour day month weekday') duplicates the schema rather than adding syntax nuance such as supported operators or how ref is parsed.

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 specific verbs and resource: turn a cron expression into plain English, validate it, compute next execution times. An agent knows exactly what it does. However, it fails to distinguish itself from the near-identical sibling dev_cron_next_runs, which appears to cover the 'next runs' half of this tool's purpose.

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?

'Use this when an agent needs to explain a cron expression and compute the next runs' essentially restates the purpose rather than giving selection criteria. No conditions, no exclusions, and no mention of dev_cron_next_runs, which the agent must choose between for the overlapping next-runs capability.

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