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

Annotations already declare readOnlyHint, idempotentHint, non-destructive and closed-world, so safety is covered structurally. The description adds nothing beyond that — no mention of what a 'definition' contains, whether definitions are scoped per contract vs. workspace, or any auth/pagination context.

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 first sentence is repeated identically, which is pure waste, and the remaining content is an operation ID plus a redirect to another tool. There is no front-loaded statement of purpose.

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?

With no output schema and no annotation gaps to fill, the description still omits what the response contains (a list of custom field definitions with types/options?) and how the per-contract scope differs from global settings custom field definitions. An agent would have to call describe_operation or probe to use it correctly.

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 0% for two parameters, so the description must compensate and it does not. The path text hints that :id is a contract identifier, but the free-form 'query' object parameter is entirely unexplained in both schema and description.

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 is a verbatim restatement of the endpoint path, duplicated, which merely echoes the tool name and title. The path does imply 'read custom-field definitions for a contract', but no prose states the verb or resource explicitly, and nothing distinguishes it from sibling endpoints like get_contracts_by_id_custom_fields_value_acf9e9f03ec0449c6dc64b8d.

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?

There is no statement of when to use this tool versus alternatives such as the custom-fields *values* endpoint or the global custom field definitions endpoint. The only usable hint is the pointer that describe_operation provides native request schemas, which is a lookup instruction rather than usage guidance.

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