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

Goes well beyond the annotations by disclosing a per-call cost ('Costs 1 credit'), the redraw path and its equal cost, the state constraint that the target mascot must be unapproved, and the required human review before approval. None of these side effects, costs, or workflow constraints are available in the structured fields.

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 short sentences, front-loaded with what the tool does, then cost, then the redraw conditional, then the workflow note. No filler or repetition.

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 correctly states that a picture is returned, covers cost and the redraw/approval flow, and the schema fully documents inputs. Minor gaps remain (image format/size, what happens on insufficient credits), but the agent has enough to call it.

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 the schema already documents all four parameters, setting a baseline of 3. The description adds a meaningful constraint the schema omits: project_id only applies to a mascot that has not yet been approved.

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 specific verb and resource ('Draws a mascot character from a description'), plus the output form ('returns the picture') and a rendering constraint ('transparent background'). This clearly separates it from siblings like add_pose, animate_mascot, and approve_mascot.

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 when to use the project_id parameter ('redraw an existing mascot that has not been approved yet') and gives a workflow instruction ('Show the user the picture before approving'), which implies the approve_mascot handoff. It stops short of naming alternatives or stating when not to call it, but the conditional usage is clear.

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