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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so safety is covered structurally. The description adds genuine context by disclosing the return content (type plus dropdown options) and the underlying endpoint GET /api/v1/CustomFields/{entityType}. It stays silent on pagination behavior beyond what the skip parameter already documents.

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?

Two sentences, front-loaded with the resource and its output shape, followed by a short usage note and endpoint. No filler or repetition of schema details.

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?

No output schema exists, and the description compensates by summarizing the returned fields, which is the key thing an agent needs. Minor gaps: it does not mention pagination defaults or the include_deleted/filter behavior, though those live in the schema descriptions.

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%, so all six parameters including the entity_type enum are documented in the schema itself. The description restates the entity_type values ('contacts, organizations (\'Group\') or users') but adds no new semantics for top, skip, filter, orderby, or include_deleted; baseline 3 is correct.

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 custom fields defined for contacts, organizations (\'Group\') or users') and even describes the payload (type Text/Dropdown plus options). The resource is distinct from every sibling list_* tool, so no disambiguation is needed beyond the entity wording.

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?

'Use the ids and option ids in the customFields of a contact or organization' tells the agent the downstream purpose — validating/selecting values before writing contacts or organizations. No explicit when-not or named alternative appears, but the sibling set contains no competing custom-field tool, so ambiguity is low.

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