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

With readOnlyHint/openWorldHint already declared, the description adds genuinely new context: it returns both a public page and a PNG in three aspect ratios, and it explicitly disclaims verification, perk granting and social publishing. The privacy warning about tokens and coupon codes is above-average behavioral guidance. It stops short of noting whether a generated card is stable/retrievable or how long the public page lives.

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?

Three sentences, zero filler: purpose first, output shape second, boundaries and safety third. Front-loaded and every clause carries a distinct fact.

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 steps up by naming the return artifacts (public page, PNG, three sizes) and by ruling out verification and publishing. The nested fields parameter is covered by the schema's own description, so little is missing for correct invocation; theme and site handling are the only thin spots.

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 only 40%, and the nested fields object is well documented in the schema itself (per-template field lists). The description contributes only the three size names plus a general note that text is supplied, leaving theme, site backlink behavior, and template-to-field mapping to the schema. Adequate but not compensating for the coverage gap.

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 ("Make a card") and enumerates the five card kinds it covers (win, streak, perk, giveaway entry, winner announcement), which maps cleanly to the template enum. It does not differentiate itself from the sibling make_winners_card, so an agent choosing between the two gets no help from this sentence.

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?

"Uses supplied text; it does not verify a winner, grant a perk or publish a social post" is a useful negative boundary that tells the agent not to expect verification or side effects. However there is no explicit guidance on when to pick this over make_winners_card, create_giveaway, or create_perk, and no prerequisites are stated.

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