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

With no annotations, the description carries the burden of disclosing behavior. The verb 'List' implies a read-only operation, and the phrase 'with descriptions' suggests the output includes both expressions and explanations. However, it doesn't disclose any additional behavioral traits such as ordering, pagination, or whether the list is exhaustive, leaving room for ambiguity.

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 a single, well-structured sentence with no wasted words. It front-loads the action ('List') and directly states the resource and what is included, making it easy to parse quickly.

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?

The tool is simple with no parameters, no output schema, and no annotations. The description adequately conveys the purpose and implies the return structure (expressions and descriptions). It could explicitly state the output format (e.g., list of objects), but the current phrasing is sufficient for this low-complexity tool.

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 input schema has no parameters, so schema coverage is trivially 100%. With zero parameters, the description need not explain parameter semantics. It does add context by specifying that the expressions are 'commonly used' and paired with descriptions, which clarifies the intended content.

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 uses the specific verb 'List' with a clear resource ('commonly used cron expressions') and indicates that descriptions are included. This clearly distinguishes it from siblings like generate_cron, which creates new expressions, and explain_cron, which explains a specific expression.

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 says what the tool does but provides no guidance on when to use it versus alternatives. There is no mention of exclusions or conditions, and sibling tools are not referenced. For example, it doesn't clarify if users should use this to find examples versus generate_cron for custom expressions.

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