set_fields

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

The description goes beyond the idempotentHint annotation by explaining field type mapping (string->text, number->number with integer coercion, boolean) and warning about float values causing API 500s. It also clarifies that untouched fields are preserved, providing valuable behavioral 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 description is concise, with the purpose stated in the first sentence and implementation details in the second. Every sentence carries useful information without redundancy.

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 two-parameter tool, the description covers the key behaviors: create/update, type selection, coercion caveat, and preservation of existing fields. The output is not described, but given the absence of an output schema and the nature of a mutation tool, the description is sufficiently complete.

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?

The input schema has no descriptions (0% coverage), so the description fully compensates by explaining the `fields` object mapping and the `identifier` parameter's accepted forms ('assetId / alias field / exact name'). This adds critical meaning beyond the raw 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?

The description clearly states 'Create or update custom fields on an existing item' with a specific verb and resource. It identifies the tool's scope (custom fields) and the target (existing item), distinguishing it from sibling tools like set_tags or set_item.

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 implies usage for updating custom fields via upsert semantics, but it does not explicitly name alternative tools or state when not to use this tool. Clear context is given, but no exclusions or alternatives are mentioned.

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