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

Annotations already declare the full safety profile (readOnly, idempotent, non-destructive, open-world). The description adds genuinely new context: pagination behavior and that totalCount is returned. However, it says nothing about cursoring beyond what the schema already covers.

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?

Three terse fragments with the resource scope front-loaded and no filler. The trailing 'GET /contacts/fields.' is weakly useful for agents that reason about REST paths but is borderline noise.

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 simple read-only list tool with full schema coverage and annotations carrying the safety profile, the description covers what is needed: what is listed, that it is paged, and that totalCount comes back. No output schema exists, and the description could go slightly further on the returned shape.

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% and both parameters are richly documented in the schema itself (page_size bounds and cursor semantics). The description adds no parameter-level detail, 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?

States the specific resource ('organization-wide contact fields shown on every contact'), which distinguishes it from siblings like list_contacts and list_contact_tags. The phrasing is a noun phrase rather than a verb, but the title supplies 'List' and the scope is 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?

No guidance on when to call this versus list_contacts, list_contact_tags, or any other sibling. The agent must infer that this returns the field *definitions* rather than field values on a specific contact.

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