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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), and the description goes well beyond them: it enumerates the full return payload (mm, in, pt, pixels at 72/96/300 ppi, aspect ratio, area, nearest standard sizes with deltas, ISO relationships) with no output schema present. It also discloses a precision caveat — "ISO values are the published whole-millimeter figures" — which is exactly the kind of subtle behavior an agent could otherwise get wrong.

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?

Three front-loaded sentences: purpose, inputs, outputs. The long name enumeration and ppi list are dense but each item is actionable information an agent needs to construct or interpret a call. Slightly list-heavy, but there is no filler sentence.

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 4-parameter, zero-required, annotation-covered conversion tool with no output schema, the description covers inputs, output shape, and numeric conventions — enough to call and interpret it correctly. The remaining gap is fallback behavior (all parameters optional: what a no-arg call returns) and how invalid size names are reported.

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%, so baseline would be 3, but the description meaningfully extends the schema by listing the complete accepted vocabulary (A0–A10, B0–B10, C0–C10, Letter, Legal, Tabloid, Ledger, Executive, Statement, Junior Legal, ANSI C/D/E, Arch A–E, DL, business cards) where the schema only offers "e.g. A4, Letter, B5, C6". It does not address precedence when both `size` and `width`/`height` are supplied, or what happens if neither is given.

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?

Opens with a specific verb+resource ("Convert paper sizes") and immediately bounds the scope to named standard sizes or custom width/height with a unit, so an agent can tell this is a pure geometry/unit conversion utility rather than a print-spec auditor. It does not explicitly contrast itself with adjacent siblings like calc_print_spec or calc_print_resolution, which keeps it from a 5.

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 two input modes ("pass `size` by name... or pass custom `width` and `height` with `unit`") imply how to call it, but there is no statement of when to prefer this over calc_print_spec or plan_imposition, and no when-not-to-use guidance. Usage is inferable but never stated as a selection rule.

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