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

Annotations already declare readOnly, idempotent, and non-destructive behavior. The description adds useful context beyond that: the approximate entry count, the shape of the response, and the fact that it takes no parameters. This is meaningful supplementary detail for a simple read tool.

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 description is information-dense with no filler. It front-loads the main purpose, then efficiently covers response contents, alternative tools, and usage relevance in a compact format.

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 zero-parameter read-only tool with an output schema and rich annotations, the description is complete. It tells the agent what comes back, how much, how it is organized, and how it relates to the rest of the API.

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 input schema contains zero parameters, so the baseline is 4. The description reinforces this with 'Takes no parameters' and adds no unnecessary parameter information, which is appropriate.

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 clearly states the resource: every Apollo field, standard and custom, returned as `fields` and `field_groups`. It includes specific attributes of the entries and explicitly distinguishes itself from `get_apollo_typed_custom_fields`, making the purpose unambiguous.

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?

It explicitly frames this tool as the reference for what can be filtered or written elsewhere in the API, which tells an agent when to reach for it. It also names the smaller alternative for custom fields only, providing a clear routing decision.

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