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

readOnlyHint=true already tells the agent this is a safe read, so the bar is lower. The description adds useful scope (the three entity types whose fields are returned) and the underlying endpoint, but says nothing about result size, pagination behavior, or whether paginated results require iterative calls even though a page parameter exists.

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?

Two short, front-loaded sentences with no filler. The trailing 'Trengo: GET /custom_fields.' is mildly redundant metadata, but it is compact and does not obscure the core statement.

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 simple read-only list tool with complete parameter coverage and annotations carrying the safety profile, the essentials are present. However, with no output schema the description could reasonably indicate what the returned field objects look like or that results are paginated, which it does not.

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 100% and the single 'page' parameter is fully documented in the schema, so the baseline is 3. The description adds no pagination or default-page semantics beyond what the schema already states.

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?

States a specific verb (List) and resource (custom fields), plus the scope of where those fields apply: tickets, contacts and profiles. This is clearly distinguishable from sibling list tools such as trengo_list_labels, trengo_list_teams or trengo_list_users, though it never names an alternative explicitly.

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 only says what the tool returns; it gives no conditions for when to call it, no prerequisites, and no guidance on when another sibling (e.g. trengo_get_contact or trengo_get_ticket_details_report) would better answer the need. Usage must be inferred entirely from the name.

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