Field values

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is fully carried by structured data. The description adds only the return semantics ('distinct values'), with no mention of pagination, result caps, or auth requirements; acceptable but adds little beyond 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?

Four labeled, front-loaded fragments (Purpose / Not for / Returns / Use when) with no filler. Every sentence carries distinct information and the routing constraint is placed early.

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 one-parameter read tool with no output schema, the definition covers purpose, disambiguation from the nearest sibling, and the shape of the return value. Nothing an agent needs to select or invoke it correctly is missing.

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% with a single required 'field' parameter, so the schema already documents the input. The description reinforces that the field is a custom field name but adds no format, naming-convention, or validation detail beyond the schema. 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?

States a specific verb (List) and resource (distinct values in one custom field) with a clear scope restriction ('one custom field'). It also explicitly distinguishes itself from the sibling plunk_get_field_usage, so an agent can route correctly without opening either 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?

Provides an explicit 'Not for' clause naming the alternative tool (plunk_get_field_usage) and its differing purpose, plus a 'Use when' clause describing the triggering scenario (building a segment filter). Both when-to-use and when-not-to-use are covered.

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