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

Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so safety is covered. The description adds value beyond that by disclosing the shape of the returned records, including the enumerable type values (text, number, date, checkbox, select, url) and the conditional 'options' field for selects — context an agent cannot get from 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?

A single tight sentence, front-loaded with the verb and resource, then the return fields, then the alternative-tool pointer. Every clause earns its place with no repetition of the title or annotations.

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?

Because there is no output schema and no parameters, the description must carry the return-shape burden, and it does: it lists the returned attributes and type values. A mention of ordering, workspace scoping requirements, or whether archived fields are included would push this to a 5.

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?

The tool takes zero parameters, so the schema imposes nothing to explain and the baseline of 4 applies. The description correctly spends its words on output semantics instead of inventing parameter guidance.

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 and resource ('List the workspace's custom task fields') and enumerates exactly what is returned: id, name, the type enum, and select options. This makes it immediately distinguishable from the sibling list_custom_field_values, which the description explicitly names as the tool for values.

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 closing sentence, 'Values are read with list_custom_field_values,' gives a clear routing rule: use this tool for field definitions, use the sibling for per-task values. There are no explicit exclusions or preconditions, but in a zero-parameter read tool that is a minor gap.

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