list_custom_fields

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

Annotations already declare readOnlyHint=true, covering safety. The description adds meaningful behavioral detail: the two modes, the cap at `limit`, and the return shape ({"total", "values"}) for field mode. It omits edge cases like pagination or error responses, but for a read-only list tool this is sufficient context beyond annotations.

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 core purpose, and no extraneous text. Every clause adds value: the two modes, the cap, and the use-case hint are all essential and efficient.

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 tool with 2 optional params and no output schema, the description covers the main return shapes (names list, and values object with total/values). It also gives usage context via sibling references. The only gap is the exact return format for the no-arg mode, but that is minor given the simple nature of the output.

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 coverage is 0%, and the description fully compensates by explaining both parameters: `field` toggles between listing names and values, and `limit` caps the result count. It adds semantics beyond the bare schema types and defaults, making parameter behavior unambiguous.

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 tool's purpose: discovering custom-field schema, with two modes (no arg vs field) and a specific verb 'Discover'. It distinguishes from siblings by explicitly mentioning set_fields/field_index as related tools, making its role in the workflow clear.

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 description explicitly says 'Useful before set_fields/field_index on an unfamiliar instance', providing direct usage guidance. It also explains when to use each mode: no arg for all field names, with field for distinct values, which helps the agent decide.

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