card_cover_set

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

No annotations are supplied, so the description carries the full behavioral burden. It discloses the destructive-adjacent case (clearing the cover) and implies the attachment must already exist, but says nothing about the previous cover being replaced, auth/permission requirements, or idempotency of repeated calls.

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?

A single front-loaded sentence with zero filler; the conditional trigger is placed first and each clause corresponds to a real mode of the tool. Nothing is repeated from the schema.

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 4-parameter mutation tool with no annotations and no output schema, the description covers purpose and triggers but omits what changed state looks like afterwards, whether prior cover settings (size/brightness) survive a re-set, and error conditions such as an attachment id that isn't on the card.

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 description coverage is 100% and every parameter (cardId, attachmentId, size, brightness) is documented in the schema, including enum meanings and the null-to-clear convention. The description adds only the framing that the attachmentId must reference an existing attachment; baseline 3 is appropriate when the schema does the heavy lifting.

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+resource (setting a card cover) and enumerates the three operations: attaching an existing attachment id as cover, changing display size, and clearing the cover. An agent can identify the action without opening the schema. It stops short of naming the sibling attachment tools that must run first (card_attachment_upload / card_attachment_add_url), so it is clear but not sibling-differentiated.

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?

The leading 'Use when...' clause lists three concrete trigger conditions that map cleanly to the tool's three modes, which is real selection guidance. It gives no exclusions or explicit statement of prerequisites (e.g. that the attachment must already exist on the card), leaving the *why-not* side implicit.

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