Put the email variables in .env

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

With only `openWorldHint: false` in annotations, the description carries the full behavioral burden and does so well. It discloses replacement semantics (existing variables replaced, everything else kept), a side effect (.gitignore is updated), secret-handling requirements, the return shape, and the authentication prerequisite involving the token saved by `login`.

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 definition is front-loaded with the core action and return behavior, and every clause adds useful information about security, prerequisites, or side effects. It is slightly dense and run-on in places, but there is no filler or repetitive content.

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 secret-writing operation with no output schema, the description is complete enough to call correctly. It covers prerequisites, authentication, file mutation behavior, security constraints, and return values, leaving no major operational gap.

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 100%, so the two parameters are already documented in the input schema. The description adds context that the file lives in the project directory but does not elaborate on syntax, defaults, or path constraints beyond what the schema provides. This is the expected baseline when the schema does the heavy lifting.

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: write named email variables into a .env file and return only the written names. It distinguishes itself from nearby tools by explicitly saying not to copy the variables into `set_env`, and its scope as an email-specific env writer is clear against siblings like `set_env_from_file` and `database_env_to_file`.

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?

It gives explicit when-to-use guidance: email must be set up first via `email_create`, and the variables must not be copied into `set_env`. It also states a clear operational exclusion: do not read the file back out to the user, because the relay token must never enter the conversation.

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