isolate_foreign

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

With no annotations, the description carries full burden. It discloses that the tool modifies text by adding Unicode bidi isolates, and the example shows the effect. However, it could mention that the original text content is preserved aside from the wrapping, but overall it's sufficient for a text transformation.

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 a single sentence with an example, containing no unnecessary words. Every part is informative and earns its place.

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?

Given the tool's simplicity (one required parameter, no output schema), the description explains the purpose, usage, and behavior completely. No additional context is needed.

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 input schema has 100% coverage with a description for the `text` parameter. The tool description adds value by providing an example and listing the types of foreign runs (phone numbers, Latin text, URLs) that should be isolated, going beyond 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 clearly states the tool wraps foreign/LTR runs inside Arabic text with Unicode bidi isolates, using specific examples like phone numbers and URLs. It distinguishes itself from sibling tools which deal with formatting numbers, plurals, etc., rather than bidi handling.

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 provides a clear use case (rendering foreign text correctly in RTL contexts) with an example. While it doesn't explicitly state when not to use or mention alternatives, the sibling list makes this tool unique for bidi isolation, so the guidance is adequate.

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