perseus

perseus_env

Read-only

Resolve environment variables for AI workspace context by embedding them with JSON Schema validation, fallback values, and required enforcement.

Instructions

Embed environment variable

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "perseus_env"
  }
}

Input Schema

Name	Required	Description
`schema`	No	JSON Schema to validate the env var value against
`fallback`	No	Value to use when the environment variable is not set
`required`	No	If 'true', render fails when the variable is unset

Output Schema

Name	Required	Description
`value`	No	Resolved value or fallback
`source`	No	Where the value was resolved from
`variable`	No	Environment variable name

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv1.0.10Jun 27, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "source": {
+      "description": "Where the value was resolved from",
+      "type": "string"
+    },
+    "value": {
+      "description": "Resolved value or fallback",
+      "type": "string"
+    },
+    "variable": {
+      "description": "Environment variable name",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

Changed3 schema fields changedv1.0.7Jun 10, 2026

changedInput schema / properties / fallback / description

Previous value: -"fallback= modifier for @env"New value: +"Value to use when the environment variable is not set"

changedInput schema / properties / required / description

Previous value: -"required= modifier for @env"New value: +"If 'true', render fails when the variable is unset"

changedInput schema / properties / schema / description

Previous value: -"schema= modifier for @env"New value: +"JSON Schema to validate the env var value against"

First observedv0.1.0May 27, 2026

TDQS

C2.2/5.0

Behavior2/5

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

Annotations provide readOnlyHint, but description adds no behavioral context beyond that; does not disclose side effects, permissions, or return behavior.

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

Conciseness2/5

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

Extremely concise (three words) but at the cost of informativeness; too terse to be useful.

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?

Despite having an output schema, the description lacks context about tool behavior and integration with other tools; minimal for a tool with many siblings.

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 100%, so baseline is 3; description does not add any extra meaning over the schema.

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

Purpose2/5

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

The description 'Embed environment variable' is vague; it does not clearly state what the tool does or how it differs from siblings like perseus_read or perseus_get_context.

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

Usage Guidelines2/5

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

No guidance on when to use this tool versus alternatives; no when-not or exclusions mentioned.

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