js

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

With no annotations provided, the description carries the full burden and does well: it discloses non-JSON-serializable value handling (Infinity/NaN/-0/BigInt decoded back to Python values, no raw dict), the auto-retry-on-Illegal-return behavior, and error handling (page exceptions → ok:false, no fake success). This is rich behavioral context beyond what any annotation could provide.

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 primary purpose and example first, then behavioral details. It's dense but information-rich — each sentence adds value. Slight room for improvement in structure but overall efficient for the amount of behavioral disclosure it conveys.

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 tool with a single parameter, no output schema, and no annotations, the description is quite complete: it covers execution semantics, return-value edge cases, error handling, and the return-statement workaround. It could optionally mention whether the code parameter supports async/await or whether mutations persist, but for a one-param JS execution tool this is strong coverage.

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?

With only 1 parameter at 0% schema description coverage, the description partially compensates by showing an example usage (`js("document.title")`) that demonstrates the expected code format. However, it doesn't explicitly document edge cases for the `code` parameter (e.g., what kind of code is valid versus invalid beyond the eval/return distinction), so it relies on the simple single-parameter 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 clearly states the tool executes JS on the current page and returns the completion value, with a concrete example (`document.title`). It distinguishes itself from siblings like `exec_python` (which runs Python) and `cdp` (which uses Chrome DevTools Protocol) by being specifically about in-page JavaScript execution.

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 the core mechanics (bare expressions evaluated directly, `return` statements wrapped in a function) which implies usage, but it doesn't explicitly state when NOT to use this vs. alternatives like `cdp` for low-level DevTools access or `exec_python` for Python. However, the JS-specific nature is reasonably clear from context, and the return-wrapping behavior is a useful guideline.

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