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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds the master API key requirement, which is useful context, but it does not describe field scope, listing behavior, or how it differs from the sibling create/typed-field tools.

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?

The useful content is front-loaded in two short sentences, and the pricing block is boilerplate rather than explanation. It is appropriately sized overall, though the HTML pricing comment is noise for tool selection.

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?

The tool is simple, has an output schema, and is covered by annotations, so the description is close to sufficient. However, it omits sibling routing and leaves the title's 'Create a Custom Field' claim unresolved, which could confuse an agent choosing between get_apollo_fields and post_apollo_fields.

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?

There are zero parameters, so the schema already fully defines the call shape and no parameter semantics are needed. The baseline for a zero-parameter tool is 4; the description adds no parameter detail but does not need to compensate for any schema gap.

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 states a clear verb and resource: 'Get a list of fields.' It does not, however, distinguish this tool from siblings such as post_apollo_fields or get_apollo_typed_custom_fields. The title's '+ Create a Custom Field' also introduces ambiguity that the description itself does not resolve.

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 only guidance is the prerequisite 'Requires a master API key.' There is no explanation of when to use this tool versus siblings like post_apollo_fields for creation or get_apollo_typed_custom_fields for typed custom fields.

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