Tool Types

When you create a tool on Rival, the first decision is the tool type. The type sets the shape of your tool - what its inputs look like, who calls it, and what kind of work it does. You pick one from the Tool Type dropdown in the initial Basic Info step of the Tool Creation flow.

Rival currently supports three tool types: Function, MCP, and Storm.

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Function

A Function is the general-purpose tool type. You define a handler (the first entry point of the function code, or the main function as the developers call it), declare its input schema, and Rival exposes it as a callable endpoint. Most tools on the platform are Functions.

Use a Function when your work fits the pattern input in, result out:

• Text processing and generation
• Classification or extraction
• Data transformation
• Analysis and summarization
• Automation steps in a larger pipeline

Tip

If you’re not sure which type to pick, start with Function. It’s the most flexible and works for the majority of use cases.

See Functions for how to write one.

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MCP

An MCP tool is a server that follows the Model Context Protocol - the open standard for exposing capabilities to AI agents and IDE assistants.

Unlike Functions, MCP tools are rarely called by humans directly. They’re consumed by:

• AI agents that need access to your data or actions
• IDE assistants (Claude Desktop, Cursor, and similar)
• Other automated systems that speak MCP

Pick MCP when you’re building a capability that should be available to AI systems rather than executed as a one-off call.

See MCP Servers for how to build one.

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Storm

Storm is Rival’s content classification tool type. It maps unstructured content - documents, articles, transcripts - against a taxonomy you provide, called a topic file.

The workflow:

1. Upload a topic file describing your categories and labels.
2. Send Storm content to classify.
3. Get back tagged output.

Storm is built for high-volume tagging - dataset preparation, content moderation pipelines, metadata extraction at scale. It is not meant for single-shot text generation; use a Function for that.

See Storm for the full guide.

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Choosing between them

Tool type	Best for	Called by
Function	General-purpose execution, transformation, analysis	Humans, apps, agents, other tools
MCP	Exposing capabilities to AI systems via MCP	Agents, IDE assistants
Storm	Large-scale content classification against a taxonomy	Pipelines, batch jobs

Note

The tool type is locked when you create the tool. If you need a different type, create a new tool.