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

Goes well beyond the annotations: it discloses the x402 USDC / card-key billing model, that the first 25 calls are free and failed calls are free, and explicitly reconciles the readOnlyHint=false annotation ('not marked read-only because each call is charged'). That reconciliation of an otherwise-confusing annotation is exactly the kind of context the description should supply.

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-loads the core purpose and the example, then appends pricing and annotation context. It is dense but each sentence carries functional information; the pricing clause is a bit of a non-behavioral addendum but is useful for the caller.

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 compute-only tool with full schema coverage and no output schema, the description covers input format, timezone, return concept, and constraints. A brief note on output shape isn't strictly needed since 'next run times' is self-evident, but nothing critical is missing.

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%, so the baseline is 3, but the description adds real meaning: UTC output, the 5-field format with ranges/lists/steps/names, and a worked example showing expr, count, and from used together. This clarifies format expectations the terse schema labels do not.

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 a specific verb (compute/return) and resource (next run times of a cron expression) with clear scope. It even pins down the accepted cron dialect (5-field, ranges/lists/steps/names) so the agent knows exactly what the tool handles. No sibling overlaps with this behavior.

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?

Explicitly says to 'check a schedule before deploying it,' giving a concrete use context. There are no sibling tools that compute cron schedules, so no alternative needs to be named, but it stops short of stating when-not-to-use.

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