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

Annotations only declare it is a non-read-only, non-idempotent, open-world write; the description goes well beyond by disclosing the 4 MB transport ceiling, the ~3 MB base64 practical limit, the mandatory no_controlled_data compliance gate (CUI/ITAR/export-controlled), and the asynchronous lifecycle (returns status 'pending', poll get_part until 'ready'). It does not contradict any annotation.

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?

Four sentences, front-loaded with the capability and formats, then limits, then the compliance prerequisite, then the async follow-up. Every sentence carries a distinct, load-bearing fact; nothing is padded or restated.

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?

Output schema exists so return values need not be spelled out, yet the description still flags the 'pending' status and the polling step, which is the piece an agent actually needs to act on. Combined with the size limits and the compliance gate, nothing required to invoke this correctly is missing.

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 the baseline is 3, but the description adds real meaning on top: it explains that filename is required when using base64 and that no_controlled_data is a compliance assertion about export-controlled data rather than a mere flag. It does not add format or syntax detail for the url field itself.

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?

Specific verb ('Upload') plus resource ('a CAD file') with the accepted formats enumerated (STL, 3MF, OBJ, STEP) and the two input channels named. An agent can distinguish this immediately from siblings like get_part, get_upload_url, or create_quote without opening any 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?

Explicitly states the decision rule between the two modes: base64 works for files up to about 3 MB due to the 4 MB MCP request cap, while 'use a URL or get_upload_url for larger files' names the alternative sibling and the condition that selects it. It also states the filename-required-for-base64 precondition.

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