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

Beyond the annotations (readOnly=false, destructive=false), the description discloses that server-managed fields are refused, that a per-second model is priced from duration and resolution, that no credits are consumed, and the exact auth requirement (OAuth or Bearer API key). This is substantial behavioral context that the annotations alone do not convey.

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?

The purpose is front-loaded and every sentence carries information (card-type fields, refused fields, pricing order, auth). It is dense rather than padded, though the auth block is somewhat long and the whole thing runs as one paragraph.

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?

For a mutation tool with nested objects, the description covers edit scope, merge behavior, server-controlled fields, pricing implications, and authentication. An output schema exists, so return values need no explanation, and nothing required to invoke the tool 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 the baseline is 3, but the description adds real meaning by listing which fields belong in data for each card type (e.g., prompt/model/aspect_ratio for generation cards, label for frames). The merge semantics are also reinforced here, exceeding what the generic object schema provides.

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 description opens with a specific verb and resource ("Change a card") and then enumerates exactly what is editable per card type (text, generation, media, frame) plus move/resize. This lets an agent distinguish it from the add_* and move_cards siblings 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?

It gives clear context for use (merging data, moving, resizing) and useful preconditions such as "Costs no credits" and the quoting-order note. However, it never names the overlapping sibling move_cards or states when to prefer it, so the alternative selection 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.