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OBS MCP

OBS MCP

by Tom-R-Main
OverviewSchemaSourceRelated ServersDiscussionsAdmin
Rust
Hybrid

Set Input Volume

obs-set-input-volume
Idempotent

Adjust a specific OBS input's volume by setting a decibel value (-100 to 26) or a multiplier (0-20). This tool provides direct audio level control for any OBS source.

Instructions

Sets the volume setting of an input

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": {
      "inputName": "<inputName>"
    },
    "name": "obs-set-input-volume"
  }
}

Input Schema

NameRequiredDescriptionDefault
inputNameYesName of the input to set the volume of
inputVolumeDbNoVolume setting in dB (-100 to 26)
inputVolumeMulNoVolume setting in mul (0-20)

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observedv1.1.1

TDQS

B3.4/5.0
Behavior3/5

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

Annotations already indicate this is not read-only and is idempotent, providing safety profile. The description does not add much beyond that, but it doesn't contradict anything. It lacks information about failure modes, authentication requirements, or default behavior when only one of the volume parameters is provided. The description is adequate but doesn't enrich the annotations further.

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 a single concise sentence that is easy to parse and front-loaded with the verb. It avoids unnecessary words and conveys the primary action directly, which is efficient for an agent.

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

Completeness3/5

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

Given the moderate complexity of having two optional volume parameters and the presence of annotations, the description is minimally sufficient. It doesn't specify how to choose between dB and mul or what happens if both are provided, which could be useful. No output schema exists, so return value explanation isn't necessary, but more behavioral notes could enhance completeness.

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?

The schema covers all three parameters with descriptions, giving 100% coverage. The description text adds no extra meaning beyond the schema, which already explains each parameter. Since schema coverage is high, baseline of 3 is appropriate; no additional clarification or examples are provided in the description.

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

Purpose4/5

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

The description 'Sets the volume setting of an input' clearly uses a verb and resource, identifying its purpose. While it is clear, it does not provide additional detail to distinguish it from the sibling tool 'obs-get-input-volume' beyond the verb. It effectively conveys what the tool does, but lacks explicit differentiation or scope details.

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 context by stating it sets input volume, but it does not explain when to use this tool over alternatives or when not to use it. There is no mention of prerequisites, edge cases, or relationships to other tools like 'obs-get-input-volume'. It provides minimal contextual guidance beyond the basic action.

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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