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

With readOnlyHint=false and idempotentHint=false in the annotations, the description proactively explains the apparent mismatch: "Reads or computes only; not marked read-only because each call is charged." It also discloses cost ($0.003/call via x402 USDC or card key), the free tier, and that failed calls are free — behavioral context annotations cannot express.

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 core conversion semantics are front-loaded in the first clause, followed by usage, an example, then billing. Slightly dense with three semicolon-joined clauses on pricing, but every sentence carries information an agent needs.

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?

No output schema exists, and the example (number=2026 → roman=MMXXVI) supplies the return format. Range, direction, mutual exclusivity and cost are all covered; the only minor gap is error behavior when an out-of-range number is passed.

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 100% (baseline 3), but the description adds a worked example (number=2026, roman=MMXXVI) showing the input/output pairing and states that exactly one of the two parameters should be supplied — mutual-exclusion guidance the schema does not encode.

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 bidirectional verb+resource: convert a number (1-3999) to Roman numerals or Roman numerals back to a number. The scope and direction are unambiguous and clearly distinct from the sibling number_words, which spells numbers rather than converting to numerals.

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?

"Give either number or roman" tells the agent how to invoke it and implicitly that the two inputs are alternatives, and "Use for dates, outlines and puzzles" gives concrete contexts. It lacks an explicit negative case or a named alternative (e.g. number_words), so it falls short of a 5.

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