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

Annotations already declare readOnlyHint and openWorldHint, and the description adds genuinely useful context beyond them: DST-correct timezone handling, invalid-field detection (error behavior), and a per-call price of $0.002 USDC via x402. It does not state pagination or output shape, but pricing and validation behavior are real disclosures.

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 tight sentences, front-loaded with the primary capability and followed by supported syntax and cost. Every clause adds information; nothing is padding.

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 read-only tool with no output schema, the description conveys the return content (plain-English explanation plus upcoming run times), syntax support, DST behavior, validation, and cost. The main gap is the unexplained 'count' parameter.

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 carry the parameters, and it only partly does: it clarifies timezone semantics (any timezone, DST-correct) but never explains the 'count' parameter controlling how many run times are returned, nor the accepted expression format beyond examples.

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 (explain) and resource (cron expression) plus the secondary output (next run times). No sibling tool covers cron parsing, so no differentiation is required, and the scope (timezone-aware, DST-correct) is unambiguous.

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?

Usage is implied by the phrasing — use it to understand a cron expression or project its future runs — but there is no explicit when-to-use guidance, no exclusions, and no named alternative (e.g. schedule or timestamp) for adjacent scheduling questions.

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