Agent Reality Layer

Execute an Agent Reality capability

execute_capability

Read-only

Validate a selected capability input and begin execution. Returns the exact paid HTTP request; an unpaid request to that URL returns the x402 challenge, and a paid request returns the result.

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": {
      "capabilityId": "<capabilityId>",
      "input": "<input>"
    },
    "name": "execute_capability"
  }
}

Input Schema

Name	Required	Description	Default
`input`	Yes
`capabilityId`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedAug 5, 2026

TDQS

A4.3/5.0

Behavior5/5

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

The description adds valuable behavioral context beyond the readOnlyHint annotation by explaining the x402 payment mechanism and what happens with unpaid vs paid requests. This is critical for the agent to understand side effects and expectations.

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

Conciseness5/5

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

Two sentences efficiently convey the purpose and the unique payment behavior. No redundant information. The description is front-loaded with the main action.

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

Completeness4/5

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

The description explains the return behavior (paid/unpaid request) and the validation step, but omits input semantics and any invocation prerequisites. Given the absence of an output schema, the description does a good job for the core execution flow, but parameter details are missing.

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

Parameters2/5

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

The description provides no detail about the parameters. The input schema has 0% coverage, and the description doesn't explain what 'input' should contain or how it relates to the capabilityId. The enum itself is documented in the schema, but the generic 'input' object is left completely undefined.

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 the tool's function: validate a capability input and begin execution. It also explicitly explains the paid/unpaid request behavior, distinguishing it from sibling search_capabilities which is for searching.

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

Usage Guidelines4/5

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

The description implies usage when you have a 'selected capability', and the sibling tool search_capabilities exists for discovery. It doesn't explicitly mention when not to use or alternative tools, but the context is clear enough.

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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