list_field_values

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

With no annotations provided, the description carries full burden. It discloses sorting by count descending and that results include message counts, but doesn't go deeper into time-range behavior, query scoping, or default limits beyond what the schema explains. This is minimal but non-tautological.

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 sentences, front-loaded with the main action, and no redundant wording. Every sentence contributes: the first states what it does, the second explains when to use it and the result ordering.

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?

Given rich schema descriptions for all 10 parameters and no output schema, the description adequately covers the tool's core purpose and use case. It doesn't reiterate optional scoping features (timeRange, query, filters), but these are well-documented in the schema, and the description provides the necessary context for an agent to decide to invoke the tool.

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%, so the baseline is 3. The description adds no parameter-specific meaning beyond the schema, which already documents fields like 'field', 'limit', and time range. It reinforces the purpose but does not compensate for any gap.

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 uses a specific verb ('List') and resource ('distinct values of a field with message counts'), which clearly distinguishes it from siblings like list_streams or search_events. It also names concrete example fields, reinforcing the tool's scope.

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 phrase 'Useful for discovering available sources, environments, logger names, etc.' gives explicit context for when to use this tool. It lacks mention of alternatives or exclusions, but the stated use cases effectively guide selection.

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