open_email

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

With no annotations, the description must carry the behavioral load, and it does disclose the key trait that this hands off to the 'default email client' rather than sending directly, plus that it returns a status string. However, it omits material behavior: whether the message is actually sent, and what happens in headless/no-client environments.

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 summary sentence is front-loaded and efficient, and the Args/Returns block is scannable. The only waste is the internal 'ctx' entry, which earns no place in a caller-facing spec.

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 5-parameter tool with zero schema descriptions and no output schema, the description supplies parameter meanings and a return summary, which is close to enough. The remaining gap is the operating-environment requirement, which matters because opening a local mail client can silently fail.

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 description coverage is 0%, so the description must compensate — and it does, naming all five parameters with plain-language meanings and marking to/subject/cc/bcc as optional while body is required. It loses a point for 'ctx: MCP context', which is internal plumbing not useful to the caller.

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 states a specific verb and resource: 'Opens the default email client with your message ready to go.' It is unambiguous and clearly distinct from all siblings (job/client/movie tools), though no sibling is explicitly named as an alternative.

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?

Usage is implied rather than stated — an agent can infer this composes a message for the user to review/send, but there is no explicit when-to-use, when-not-to-use, or mention of prerequisites (e.g., a desktop mail client must exist).

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