List custom fields

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

Annotations already carry the safety profile (readOnlyHint=true, idempotentHint=true, destructiveHint=false), so the bar is lower. The description adds value by disclosing the scope (which record types the custom fields belong to) and the purpose of the returned ids, but it does not describe pagination, ordering, or response shape, and there is no output schema to fill that gap.

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 sentence of roughly nineteen words that front-loads the verb and resource and packs scope and purpose without fluff. Every element earns its place and nothing is redundant with the schema 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?

Adequate for a simple, read-only tool with one optional parameter: safety is covered by annotations, the parameter by the schema, and the resource/scope by the description. The only gap is the absence of any return-value description given that no output schema exists — a minor omission for a listing tool of this simplicity.

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% — administration_id is fully documented in the input schema, including its default and how to discover valid values. The description adds no parameter-level information, so the baseline of 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?

The description uses a specific verb ('List') and resource ('custom fields'), and names the exact scopes: contacts, sales invoices, and identities. It is easily distinguished from sibling list tools, which target different resources, and the closing phrase gives the output a clear purpose.

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 phrase 'with the ids needed to set them' signals the intended use case — retrieving ids before setting custom fields — providing clear contextual guidance. However, it names no alternative tool and states no explicit when-not-to-use condition, so the guidance is contextual rather than fully explicit.

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