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

Annotations already declare destructiveHint=true and readOnlyHint=false, so the agent knows this mutates state. The description usefully discloses that passing null clears the field, which goes beyond the annotations, but it omits what happens to the prior value, whether missing fields/options error out, and permission requirements.

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?

One front-loaded sentence: the operation first, then the type-value mapping that the agent needs. Every clause earns its place given the 0% schema coverage and the type union.

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, no nested objects, and annotations already covering the safety profile, the description covers the essential input semantics including the tricky polymorphic value. Only edge-case behavior (invalid fieldId, overwrite semantics) is unaddressed, which is minor here.

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 0% and the value parameter is a polymorphic union, so the description's format spec (text/number/select/checkbox/date with YYYY-MM-DD) genuinely compensates for what the schema cannot express. cardId and fieldId are undocumented but self-evident by name.

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 precise verb+resource (sets a custom field's value on a task) and adds that it can clear the value with null. It is clearly distinct from update_custom_field and update_task, though it does not name those siblings explicitly. An agent can identify the operation without opening the 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?

Usage is implied by the null-clearing clause and the type enumeration, but there is no explicit when-to-use/when-not guidance and no alternative tool is named. For a setter that competes with update_task and update_custom_field, more routing guidance would help.

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