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

Adds substantial behavior beyond the annotations: the per-call cost (1 generation of plan quota), the anti-retry policy, the fact that responses contain hosted URLs rather than file bytes, and the underlying POST /v2/create-image endpoint. None of that is derivable from the readOnly/openWorld/idempotent hints.

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-loads the action, then cost, then caution, then endpoint in labeled segments. Four dense sentences, no filler, and the most decision-relevant facts (what it renders, what it costs) come first.

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 six parameters, no output schema, and a clear mutation profile, the description covers the missing pieces: return shape (URLs, not bytes), quota impact, and retry guidance. An agent has everything needed to invoke it correctly and safely.

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 baseline is 3, but the description supplies a concrete overrides payload example ([{"name":"text_1","text":"Hello"},{"name":"image_1","src":"https://..."}]) that documents the free-form layer properties the schema leaves as additionalProperties with no enumeration.

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 ('renders one image') with the required template source ('from a saved image template'), and names the output formats (JPEG and PNG). The word 'image' cleanly separates it from the apitemplate_create_pdf family of siblings without needing to name them.

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?

Gives a clear when-not rule ('Do not retry or repeat it unless needed; every call is counted') and points to apitemplate_get_account for quota context. It does not explicitly contrast itself against the PDF-rendering siblings, so the choice between this and create_pdf_from_html is left to inference.

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