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

Goes well beyond the annotations by disclosing that values in custom_fields are type-validated from then on, that types are immutable once populated, and the pricing model ($0.001 per call, free on failure). The type-immutability and cost details are things no annotation fields encode, and nothing here conflicts with idempotentHint=true or destructiveHint=false.

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?

Front-loaded with the action and scope, then behavior, then the type caveat, then cost. Four sentences each carry distinct information, though the type enumeration is a little dense and partly duplicates the enum.

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 schema-less-output mutation tool, the description covers validation behavior, type immutability, and billing, which are the agent-relevant unknowns. Minor gaps remain around whether the field definition is echoed back and whether label/description default to anything.

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?

With 50% schema coverage, the description does real work: it enumerates all eight type values with the date format spelled out (YYYY-MM-DD), and mentions options, label, description, and the three target objects. Only the `key` format detail is left entirely to the schema.

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?

"Add a field of your own to contacts, companies or deals" names a specific verb and resource, and the second clause extends the scope to relabeling/editing existing fields. An agent can separate this from crm_delete_field and crm_list_fields without opening a schema.

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 covers the meaningful decision point explicitly: "A field that holds values keeps its type; delete it and define it again to change the type." That is real when-and-how guidance, though it never names the sibling tool (crm_delete_field) an agent would need to accomplish the type change.

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