Set or delete environment variables for a service by name, using null to remove values; redeploy to apply changes.
Set or delete env vars: vars is {NAME: "value" or null}. Redeploy to apply.
| Name | Required | Description | Default |
|---|---|---|---|
| vars | Yes | ||
| service | Yes | Service id or `project.service`, e.g. `shop.api` |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full behavioral burden. It usefully discloses that null values delete variables and that a redeploy is required, but it omits permissions, overwrite/merge behavior, and whether changes are reversible.
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 compact and front-loaded, with no wasted wording. It communicates the operation, variable format, and required follow-up in one short statement.
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?
It covers the core call semantics and the redeploy requirement, but leaves important ambiguity for a mutation tool with no annotations and a nested object: whether provided vars merge with or replace existing variables, and what permissions or safety constraints apply.
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 schema documents the service parameter, while the description compensates for the undocumented vars object by explaining its exact shape: {NAME: "value" or null}. This adds important meaning beyond the schema, especially the null-delete convention.
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 or delete environment variables. It also explains the null-value deletion semantics, though it does not explicitly differentiate this tool from the sibling list_env tool.
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 a post-call requirement ("Redeploy to apply") but does not explain when to use this tool instead of alternatives such as list_env, deploy, or restart. There is no explicit usage context or exclusion guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
This server cannot be deployed