List fields

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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds useful content-level detail (that output includes configured trace fields and the error query), but says nothing about result size, truncation, or cost on large indices.

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 sentences, front-loaded with what is returned before the guidance sentence. No filler. The parenthetical and the clause about trace/error fields make it slightly denser than ideal, but nothing is wasteful.

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?

No output schema exists, so the description must carry return-value meaning; it does so by enumerating what the listing contains. For a simple read-only introspection tool with a fully documented schema and annotations, this is nearly complete, missing only result-size or pagination behavior.

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 all three parameters (contains, instance, include_internal) are already fully documented in the schema. The description adds no parameter-level meaning beyond that, which is the baseline 3 case when structured data does the work.

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+resource: listing field names and types. It also scopes the content to fields 'present in the indices' plus trace fields and the error query, which distinguishes it from siblings like list_instances or list_streams. It stops short of naming an alternative tool, so not a 5.

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?

Gives a clear usage condition: 'Use before writing queries on unfamiliar logs.' That tells the agent when this tool is the right first step. There is no explicit when-not or named alternative, so it lands at 4 rather than 5.

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