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

With no annotations, the description carries the full burden and does so well: 'Instant, no human involved, nothing is ordered' and an explicit 'It does NOT return a price and never will... Do not infer a price from the grams.' That is strong disclosure of side-effect-free behavior and a real misuse guardrail. It stops short of describing error handling or limits for unsupported files.

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 action and outputs, then the usage rule, then the negative constraint. Nearly every sentence earns its place, though the no-price point is stated twice ('does NOT return a price' and 'Do not infer a price'), a mild redundancy.

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 and no annotations, but the description compensates by enumerating what comes back (size, volume, plastic usage, plate fit) and what does not (price). Three parameters are fully schema-described. Only error/edge behavior for malformed or unsupported files is left implicit.

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 100%, so fileName, base64 and material are already fully documented — baseline 3. The description adds no new per-parameter semantics beyond the schema (the STEP-not-measurable and material-affects-weight notes are already in the field descriptions).

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?

Names a specific verb+resource ('Send an STL, 3MF or OBJ and get back its real size, volume...') and enumerates the exact outputs (size, volume, grams, plate fit). It is unmistakably distinct from submit_job, which it explicitly contrasts against.

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?

States the trigger condition plainly: 'Use this BEFORE submit_job whenever your human has a file.' It also names when-not (it never returns a price, orientation/supports/finishing are decided by a person) and points at the concrete failure cases it is meant to catch (oversized part, inch/mm unit error, non-solid mesh).

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