open_url

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

No annotations are present, so the description carries full burden. It discloses the execution mechanism (shell.openExternal), allowlisted schemes, and dangerous scheme rejection with 403. This goes beyond a basic 'opens URL' description, though it omits details like error behavior for invalid URLs.

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 four sentences, each serving a distinct purpose: purpose, mechanism, UI context, and security. It is front-loaded and contains no redundant or extraneous information.

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 simplicity of the tool (1 parameter, no output schema, no annotations), the description covers the key aspects: what, how, security. It lacks explicit return value description but rejects dangerous schemes with a status code, which provides operational context.

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 single parameter 'url' is fully described in the input schema. The tool description reiterates the allowlisted protocol requirement but adds no new semantic details beyond the schema. With 100% schema coverage, baseline 3 is appropriate.

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 it opens http/https URLs or Windy ecosystem schemes via Electron's shell.openExternal. It explicitly mentions mirroring UI buttons, distinguishing it as a general URL opener. Sibling tools like open_upgrade_checkout and open_billing_portal are more specific, but this tool covers broad use cases.

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 implies usage by stating it mirrors UI buttons, but it does not explicitly guide when to use this tool vs alternatives like open_upgrade_checkout or open_billing_portal. No exclusions or when-not-to-use guidance is provided.

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