Set or update environment variables in a Node.js application's .env file by specifying the app root and KEY=VALUE entries, so configuration changes are applied consistently.
Set or update environment variables in .env for a Node.js application
| Name | Required | Description | Default |
|---|---|---|---|
| app_root | Yes | Application root directory | |
| env_variables | Yes | List of environment variables in KEY=VALUE format (e.g. ['PORT=3000', 'NODE_ENV=production']) |
Changes observed during successful MCP inspections.
v2.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full burden for a mutating, file-writing tool. It never says whether existing .env keys are overwritten or merged, whether the file is created if absent, whether the change takes effect without a restart_nodejs_app call, or whether backups are made — all material behaviors for config mutation.
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?
A single front-loaded sentence with no filler; the resource and scope appear immediately. Brevity is efficient, though it edges toward under-specification rather than crispness.
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 mutation tool with zero annotations and no output schema, the definition omits the facts an agent most needs: overwrite/merge behavior, whether the app must exist first, and whether a restart is required. It is a thin one-liner against a task that has real side effects.
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 coverage is 100% and both parameters are documented with an explicit KEY=VALUE example for env_variables, so the schema already does the heavy lifting. The description adds no parsing rules (quoting, whitespace, duplicate keys) beyond what the schema states, making the baseline 3 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 states a specific verb and resource — set/update environment variables in a .env file for a Node.js application — which is concrete enough to distinguish it from setup_nodejs_app or configure_python_env. It stops short of explicitly contrasting itself with those siblings, so it lands at 4 rather than 5.
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?
There is no guidance on when to call this versus setup_nodejs_app, restart_nodejs_app, or configure_python_env, and no stated prerequisites (e.g. that the app must already be provisioned). 'Set or update' hints at upsert semantics but leaves sequencing and alternatives entirely to inference.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.