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

Annotations already cover safety (readOnlyHint, idempotentHint, destructiveHint=false), and the description still adds real context beyond them: leading zeros are stripped, sign is preserved, invalid input is rejected, and the call is metered at $0.001 USDC per successful call with an alternate HTTPS endpoint. The pricing/transport disclosure is behavior an agent cannot infer from annotations. It stops short of saying what the response payload actually looks like.

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 core operation, followed by edge cases, then payment and endpoint details — a sensible ordering. Every sentence carries information, though the pricing plus full URL in the description body is somewhat operational rather than semantic.

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 utility with no output schema, the definition covers the transformation, zero handling, sign handling, and rejection of bad input — enough to call it correctly. The remaining gap is the return type (string vs integer) and the 200-digit limit, which an agent would only discover from the schema.

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 carries the burden for the single parameter 'n'. It conveys the semantics through the 1200 → 21 example and explains that malformed input is rejected, but never states the 1–200 digit bound or that 'n' must be supplied as a string — the word 'integer' arguably nudges toward sending a JSON number, which the pattern-based schema would reject.

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 concrete verb and resource — 'Reverse the decimal digits of an integer' — and the qualifier 'decimal' implicitly separates it from digit-adjacent siblings such as bit_reverse or reverse_add. The worked example (1200 → 21) removes any doubt about the transformation. What it lacks is any explicit naming of a sibling it should not be confused with.

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?

There is no guidance on when to reach for this tool versus the hundreds of sibling number-theory tools, and no exclusions or prerequisites beyond payment. The sentence 'A malformed integer is rejected' describes a behavior, not a usage condition. Against a sibling list containing reverse_add, bit_reverse, and digit_sum, a routing hint would have earned a higher score.

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