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

Goes well beyond the readOnly/idempotent annotations by disclosing the paid x402 flow, the exact price ($0.001 USDC per successful call, Solana), the error behavior for out-of-range indices, and an equivalent HTTPS endpoint. Payment requirements are critical context an agent cannot infer from annotations.

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?

Semantics are front-loaded (definition, then index rule, then example), with error behavior and payment details trailing. Every sentence adds distinct information; 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?

For a two-parameter pure-computation tool with no output schema, the description covers semantics, ranges, error behavior, and cost. It could be marginally clearer that the return value is a single digit character, but the opening sentence establishes that.

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 burden, and it does: 'i' is documented as a 0-based digit index with a concrete worked example, and 'n' is documented as the term number with range 1-25 matching the schema bounds.

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 ('one digit of the nth look-and-say term') with a worked example (term 5 = 111221, index 3 = 2) that makes the operation unambiguous. An agent can tell this apart from the look_say, look_say_len, and look_say_step siblings without opening the schema.

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?

Gives clear operating context: index is 0-based, out-of-range indices are rejected, and n is bounded 1-25. It does not explicitly name the sibling alternatives (e.g., 'use look_say for the whole term'), so it earns 4 rather than 5.

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