vercel-mcp-pro

update_env_var

Update an existing environment variable by ID with new key, value, target, type, or comment. Modify Vercel project environment settings directly.

Instructions

Update an existing environment variable (value, target, type, comment) by id.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "projectId": "<projectId>",
      "envId": "<envId>"
    },
    "name": "update_env_var"
  }
}

Input Schema

Name	Required	Description
`projectId`	Yes	Project id or name.
`envId`	Yes	Environment variable id.
`key`	No
`value`	No
`target`	No
`type`	No
`gitBranch`	No
`comment`	No
`teamId`	No	Team ID to scope the request. Falls back to VERCEL_TEAM_ID when omitted.
`slug`	No	Team slug to scope the request (alternative to teamId).

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Jun 11, 2026

TDQS

B3.3/5.0

Behavior2/5

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

No annotations are provided, so the description must carry the full burden of behavioral disclosure. It only says 'update', which implies mutation, but does not disclose idempotency, overwrite behavior, permission requirements, error handling (e.g., missing envId), or rate limits. The description is insufficiently transparent.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is one sentence of 13 words, which is concise. It front-loads the action and resource. However, it could be more structured by separating the list of updatable fields or adding a note about required parameters.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness2/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given 10 parameters, 2 required, and no output schema, the description is too sparse. It does not explain return behavior, error cases, prerequisites, or how this tool differs from bulk_create_env_vars (which might also update). Critical context is missing for correct invocation.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is only 40%, with many parameters (key, value, target, type, gitBranch, comment) lacking descriptions. The description adds meaning by listing value, target, type, and comment as updatable fields, but does not cover key or gitBranch. It partially compensates for the schema gaps but not fully.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states 'Update an existing environment variable' and lists the specific fields that can be updated (value, target, type, comment). It distinguishes from sibling tools like create_env_var, delete_env_var, and get_env_var by focusing on the update operation.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies usage for updating an existing environment variable, but it does not explicitly state when to use this tool versus alternatives (e.g., create_env_var for new variables, delete_env_var for removal). No when-not or alternative tool names are mentioned.

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

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