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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), yet the description adds genuinely new behavioral context: a paid x402/USDC model at $0.001 per successful call, and an alternate HTTPS POST endpoint. It doesn't state what happens on out-of-range n or failed payment, which keeps it from a 5.

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-loaded with the one-sentence definition, then examples, domain, and operational metadata. Every sentence carries information; the range restatement duplicates the schema's min/max but earns its place by explaining the 99987 cap.

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 single-parameter tool with no output schema, the description provides the return semantics via examples, the valid input domain, and the payment/transport mechanics. Only edge-case behavior (invalid n, payment failure) is left unstated.

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 0%, so the description must carry the parameter meaning, and it does: it defines n's domain (1 to 99987), explains the upper bound's rationale ('the last lucky number through 100000'), and shows input→output examples. Only the output type of n is unspecified.

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 precise verb+resource: 'the least lucky number greater than or equal to n', backed by three concrete n→output examples (2→3, 20→21, 49→49). The operation is unambiguous and conceptually distinguishable from siblings like lucky_nth or lucky_twin, though no sibling is named explicitly.

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 semantics ('next lucky number ≥ n') strongly imply when to call it, but there is no explicit routing guidance telling the agent to prefer lucky_nth or lucky instead. No exclusions, prerequisites, or usage conditions are stated.

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