List research features (the grammar registry)

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

The annotations declare readOnlyHint and openWorldHint, but the description adds the crucial ETag-revalidation behavior, explaining that additive feature ids become visible to long-running agents. This goes beyond the annotations and provides useful operational 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?

Three sentences, each with a distinct purpose: enumerating contents, instructing to call first, and explaining caching behavior. No filler words; all sentences contribute essential information.

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?

Despite lacking an output schema, the description thoroughly enumerates what the response contains, including feature ids, dtypes, ranges, operators, window aggregates, sequence rules, limits, sort fields, and error-code lists. It also justifies the 'call first' guidance and caching, making it fully self-contained for a read-only registry 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?

The tool has zero parameters, so the baseline is 4. The description does not need to elaborate on parameters; instead, it focuses on the richness of the response. It conceptually mentions 'pinned feature_version' but does not treat it as an input parameter.

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 the tool returns the closed registry for the pinned feature_version, enumerating the specific contents (feature ids, dtypes, ranges, operators, etc.). This distinguishes it from sibling tools like list_instruments, which likely return a different registry.

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?

Explicitly instructs 'Call this FIRST' and explains why: using only ids from this registry prevents inventing field names. This provides clear guidance on when to use it, though it doesn't name alternative tools explicitly, the context implies it is the foundational reference.

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