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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), and the description adds the critical non-obvious trait: this is an internal tool reserved for the card preview view. It also scopes the result to the first card only, not the whole batch. It does not say why the restriction exists or what happens if it is called anyway.

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 short sentences, with the most decision-relevant information ('Do not call it') placed up front, followed by scope and return meaning. No filler.

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?

An output schema exists, annotations cover safety, and the one parameter is fully described in-schema. The description supplies the only thing an agent still needs: that this tool is off-limits and why it exists.

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% and the single batch_id parameter is documented in-schema with its UUID pattern and its origin ('from prepare_card'). The description adds nothing about the parameter, so baseline 3 applies.

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 names the specific resource (the rendering of the first card of a prepared card batch) and the verb (returns), so an agent can distinguish it from prepare_card or get_card_options. The phrasing 'how the first card ... is drawn' is slightly vague about whether this is a layout/render preview versus card data, which keeps it from a 5.

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 explicit negative guidance — 'Only the card preview view calls this tool. Do not call it.' — which is a rare and unambiguous when-not statement. It stops short of naming what an agent should call instead for card preview data, so it is clear context without a full alternative routing.

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