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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior, so the description's added value is what goes beyond that: results include flags, prefixes, and deprecation notes from a local snapshot, unknown data is reported as 'unknown' rather than guessed, and no account or token is needed. That is meaningful behavioral context, though it says nothing about performance limits or error cases such as a malformed path.

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?

Purpose sentence first, then a 'When to use' line, then brief notes, then a concrete example — each labeled block earns its place and nothing is repeated from the schema.

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?

With an output schema present, return values need no explanation, and annotations plus full schema coverage handle safety and parameter formats. The description fills the remaining gaps (data provenance, unknown handling, no auth), leaving only minor omissions such as behavior on invalid paths.

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 per-parameter descriptions and format patterns, so the baseline is 3. The description's example arguments add value by demonstrating the pairing of an exact BCD path with a multi-target array, reinforcing that the path must be exact and several browsers can be queried at once.

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 and resource — check browser support for an exact MDN BCD feature path at given browser versions — and names the data source (local BCD snapshot). It is clearly distinguishable from siblings like check_semver_range or check_dependencies, which answer different compatibility questions.

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?

An explicit 'When to use' line scopes it to deciding whether a web API, CSS, or JS feature works in specific browser versions. No sibling alternative or exclusion case is named, but the usage context is unambiguous.

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