OPA capabilities

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

Annotations already declare readOnlyHint, destructiveHint, idempotentHint, and openWorldHint. The description adds critical context about response size limits and the rationale for 'names_only: true' as a safeguard, going beyond what annotations provide. No contradictions with annotations.

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?

The description is two sentences long and front-loads the main purpose. It uses clear, specific language without redundant phrases. Each piece of information serves a purpose, though the second sentence could be slightly restructured for even tighter readability.

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?

The description clarifies the different response modes but does not specify the exact output structure (e.g., JSON fields, count format). Given the absence of an output schema, agents might need to infer the format from context. For a tool with moderate complexity, this is an acceptable but not fully complete explanation.

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 coverage is 100% with all three parameters described. The description adds meaning by explaining the conditional behavior: 'With current: true, returns... With version: ... returns...' and the default behavior of 'names_only'. It also warns that full specs may exceed client limits, which is not in the schema.

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 begins with a clear action verb 'Return' and specifies the exact resource: 'OPA capabilities -- the available builtins, future keywords, features, and WASM ABI versions.' It distinguishes itself from sibling tools (e.g., rego_check, rego_eval) by focusing solely on capability metadata rather than policy evaluation or checking.

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 explains three usage modes: using 'current' for the running OPA, 'version' for a specific version, and neither to list available versions. It also describes the 'names_only' parameter's effect. While it doesn't explicitly state when NOT to use the tool, the instructions are sufficiently clear for an AI agent to decide.

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