Next run times (in UTC) of a standard 5-field cron expression (minute hour day month weekday; ranges, lists, steps and names like MON or JAN supported). Use to check a schedule before deploying it. Costs $0.001 in USDC on Base per successful call, paid with x402.
| Name | Required | Description | Default |
|---|---|---|---|
| expr | Yes | The cron expression | |
| from | No | Start time, ISO (default now) | |
| count | No | How many runs (1-50, default 5) |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Adds genuinely valuable behavior beyond the annotations: output is in UTC and each successful call costs $0.001 in USDC on Base via x402. The payment/authorization detail is exactly the kind of context annotations don't carry (and helps explain readOnlyHint=false for what is otherwise a pure computation). It stops short of describing error handling for invalid expressions.
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?
Two sentences, front-loaded with what the tool returns, followed by the usage cue and cost. Every clause earns its place; nothing is redundant with the schema.
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?
No output schema exists, so the description carries the return-value burden, and it does so by stating the output is next run times in UTC. Combined with the payment disclosure and syntax notes, an agent has enough to invoke it correctly; only failure/error semantics are omitted.
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 baseline is 3, but the description adds real semantics the schema lacks: the 'expr' field is a standard 5-field expression supporting ranges, lists, steps and names like MON/JAN, and output is UTC. This meaningfully enriches the otherwise terse 'The cron expression' schema description.
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+resource: computing the next run times of a standard 5-field cron expression. No sibling does cron evaluation (unix/time/date_add are distinct), and the description specifies the exact field layout and supported syntax, so an agent can identify it immediately.
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 tells the agent when to reach for it: 'Use to check a schedule before deploying it.' This gives clear context, though it names no alternative or exclusion conditions (there is no obvious competing sibling, so the omission is minor).
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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