List Contact Custom Field Definitions

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 a genuinely useful behavioral fact beyond the annotations: the required OAuth scope 'contacts:read', which tells the agent what authorization the call needs. 'Reads Calendly data' is filler, but the scope disclosure is real added value.

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 very short sentences, front-loaded with the purpose and free of padding. 'Reads Calendly data' is mildly redundant filler, keeping it just short of a 5.

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 parameterless read-only list tool this is minimally adequate, and the annotations plus full schema coverage carry most of the burden. With no output schema, however, the description says nothing about the shape of results or pagination, which for a list endpoint would be useful context.

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 is only one optional parameter and schema description coverage is 100%, with the schema explaining that 'account' selects credentials rather than an organization URI. The description adds no parameter detail, so the baseline of 3 for schema-complete parameters 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 states the verb 'List' and the resource 'Contact Custom Field Definitions', which is a specific verb+resource pair. However, it is nearly a verbatim restatement of the tool name and title, adding no new discrimination. It does distinguish from the singular sibling get_contact_custom_field_definition only by implication (plural list vs. single get), which the name already conveys.

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 names a required scope (contacts:read), which is a precondition, but gives no when-to-use or when-not-to-use guidance and never points to alternatives such as get_contact_custom_field_definition for a single definition. An agent must infer selection from the name alone.

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