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

Annotations already indicate that this is a safe, idempotent write operation. The description adds value beyond annotations by disclosing the 'null clears a field' behavior and explicitly stating that column moves are not handled by this tool, which are important behavioral nuances not captured by the annotations.

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 description is three short sentences, each earning its place: the first states the purpose, the second gives a critical usage note, and the third directs to an alternative for a distinct use case. There is no fluff or redundancy.

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?

Given the absence of an output schema, the description might need to hint at return values, but for a card update tool, the behavior is straightforward. It covers the main operation, the null-clear behavior, and the column limitation. The required board_id and card_id are documented in the schema, so the description is sufficiently complete for selection and basic invocation.

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?

With 71% schema description coverage, the schema already documents most parameters. The description adds meaning by enumerating the fields that can be changed ('title, description, due date or colour') and by explaining the null convention, which helps agents understand the parameter semantics beyond the raw schema. It also implicitly indicates that column is not a parameter.

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 clearly states the tool changes a card's title, description, due date, or colour, with a specific verb and resource. It also distinguishes itself from the sibling tool move_card by explicitly noting that column changes should use move_card instead.

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 description provides explicit usage guidance: 'Pass null to clear a field' and 'Use move_card to change column.' This gives a clear when-to-use and a when-not-to-use (column changes) with a named alternative, making it easy for an agent to decide between update_card and move_card.

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