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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false, so the safety profile is covered by structured fields. The description adds useful behavioral context beyond that: team-scoping and the fact that definitions (not values) are returned. It stops short of describing ordering or pagination, but an output schema exists to cover the return shape.

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 short sentences with no filler: scope first, the key exclusion second, and the workflow routing last. Every sentence carries distinct, actionable information and the most important constraint is front-loaded.

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 zero-parameter, read-only list tool with full annotation coverage and an output schema, the description supplies exactly what structured fields cannot: what the data represents (definitions, not values) and how it fits into the add/update workflow. Nothing an agent needs to select or invoke this tool is missing.

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 tool takes zero parameters, which sets the baseline at 4. The description correctly implies no filtering is required or possible and adds scope framing (authenticated team), consistent with an empty schema. There is no additional parameter nuance to convey.

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 names a specific verb and resource ('List the custom-field definitions') and scopes it to the authenticated Chatway team. It explicitly distinguishes itself from a value-returning operation by stating it does not return field values for a particular visitor, so an agent won't confuse it with per-visitor data retrieval.

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?

It gives an explicit when-to-use rule: call this before `add-custom-data` or `update-custom-data` to reuse existing field names. It also carves out the negative case ('does not return field values'), which prevents misuse by agents looking for visitor data. The sibling alternatives are named directly.

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