Autofill a Canva template

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

Beyond the annotations (which only flag non-readonly, non-idempotent, open-world), it discloses that a new design is created each time, that media is uploaded to Canva first, the required account tier, and that the response is the new design's edit link. That is exactly the kind of side-effect and auth context annotations can't carry.

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 action and the 'NEW design' constraint, then preconditions and return value; every sentence carries information. The telegraphic fragments ('Free.') are efficient but slightly clipped.

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?

With no output schema, the description still names the return value (edit link), and it covers the plan gate, media handling, and the create-not-mutate behavior. Nothing an agent needs to invoke it 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 coverage is 100%, so baseline would be 3, but the description adds real semantics for the `data` object: values are either text or an image/video expressed as a Library id or link. That goes meaningfully beyond the schema's bare '{ field: value }' and is the main source of call errors otherwise.

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?

The first sentence states a specific verb (fill), resource (Canva brand template fields) and a scoping constraint that matters: results go into a NEW Canva design rather than editing the template. That distinguishes it cleanly from siblings like list_canva_brand_templates and save_to_canva.

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?

It gives a clear entry point ('brandTemplateId from list_canva_brand_templates') and states the plan precondition (Pro/Teams/Enterprise), which tells the agent when the call is viable. It stops short of naming when to prefer save_to_canva or export_canva_design instead, so no explicit exclusions.

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