api_cron_parseExplain a cron expression: next 3 run times in UTC. ?expr=*/5 * * * * [HTTP x402 price: $0.001]
| Name | Required | Description | Default |
|---|---|---|---|
| params | No |
| Name | Required | Description | Default |
|---|---|---|---|
No arguments | |||
Changes observed during successful MCP inspections.
Input schema / properties / params / additionalPropertiesRemoved value: -trueInput schema / properties / params / propertiesAdded value: +{
+ "expr": {
+ "anyOf": [
+ {
+ "type": "string"
+ },
+ {
+ "type": "null"
+ }
+ ],
+ "default": null
+ }
+}Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden. It discloses useful behavior: output is limited to 3 run times, expressed in UTC, and priced at $0.001 via HTTP x402. It does not disclose behavior on invalid or extended cron syntax (e.g., seconds field, @macros), which a parser tool should ideally cover.
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 tightly packed: purpose, output scope, example, and pricing all in one short sentence plus fragment. No filler words, and the core purpose is front-loaded. The price note is unusual but earns its place as cost-relevant operational context.
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 simple one-parameter tool with an output schema present, the description covers the essentials: what it does, what it returns (3 UTC run times), and how to invoke it. An edge-case statement about invalid expressions would round it out, but nothing critical blocks a correct first call.
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 0%, so the description must compensate. The example '?expr=*/5 * * * *' demonstrates the expected cron expression format, and the parameter name 'expr' is self-explanatory. However, it does not specify valid field counts, supported macros, or escaping rules, leaving partial ambiguity.
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 description states a specific verb and resource: 'Explain a cron expression' with a precise output scope ('next 3 run times in UTC'). This clearly distinguishes it from all sibling utilities, none of which relate to time expression parsing.
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 sentence and the concrete example (?expr=*/5 * * * *) imply when to use the tool, and no sibling tool competes for the same job. However, there is no explicit guidance on prerequisites, valid expression variants, or exclusions, leaving some inference to the agent.
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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