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

The description goes beyond the annotations by explaining the resolution behavior for loose names, the exact outputs returned (earliest continuously-supported version per browser, global usage percentage, safe_to_use flag), and the conservative nature of the flag. This gives the agent a solid mental model of what will happen without needing to invoke the tool.

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 compact and front-loaded with the core question, then provides concrete examples and output details, and ends with a clear usage directive. Every sentence contributes useful information without redundancy.

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 single-parameter, read-only tool with a full output schema and strong annotations, the description is complete. It covers what the tool does, how the input is interpreted, what outputs to expect, and when to use it, so an agent can select and invoke it correctly with minimal uncertainty.

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 schema already provides 100% coverage for the single parameter, explaining that it accepts a feature name or caniuse id and that loose names are resolved. The description adds extra examples like ':has()' and 'container queries', but these largely reinforce the schema rather than introducing meaningfully new semantics.

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's function: it accepts a loose feature name, resolves it to a caniuse feature, and returns browser support versions, usage percentage, and a safe_to_use flag. This is specific and differentiates from siblings like search_features and get_feature_by_id, as it answers the full support question directly.

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 explicitly says 'Use this first; it answers the whole question in one call,' giving clear priority and context for when this tool is appropriate. It does not explicitly state when to choose get_feature_by_id or search_features instead, but the guidance strongly implies this tool is the primary entry point for feature-support questions.

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