x402-alpha

alpha_subscribe

Create a notify-on-condition webhook subscription: 5 prepaid HMAC-signed deliveries when a price/funding condition triggers. $0.05 USDC ($0.01 per delivery, prepaid). Payment is consumed on execution.

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": {
      "type": "<type>",
      "symbol": "<symbol>",
      "threshold": "<threshold>",
      "webhook": "<webhook>"
    },
    "name": "alpha_subscribe"
  }
}

Input Schema

Name	Required	Description
`type`	Yes	Condition type: price_above, price_below, or funding_above_abs
`symbol`	Yes	Asset symbol (e.g., SOL)
`webhook`	Yes	HTTPS webhook URL on a public host
`threshold`	Yes	Trigger threshold (price in USD, or absolute funding rate)

Schema Changelog

Changes observed during successful MCP inspections.

First observedJun 11, 2026

TDQS

A4.2/5.0

Behavior4/5

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

With no annotations, description carries full burden and discloses key behaviors: prepaid HMAC-signed deliveries, limit of 5 deliveries, $0.05 USDC cost, payment consumed on execution. Missing details like handling of never-triggering conditions or webhook failures.

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 with no wasted words. Front-loaded with core purpose and immediately followed by critical operational details.

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?

Description adequately covers purpose, mechanism, and cost. However, missing return value (e.g., subscription ID or confirmation) reduces completeness for agent invocation without output schema.

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 covers all 4 parameters with descriptions (100% coverage). Description adds marginal value by tying parameters to the payment model and delivery count, but does not significantly enhance parameter meaning beyond schema.

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?

Description clearly states 'Create a notify-on-condition webhook subscription' with specific verb and resource, and distinguishes from sibling tools (e.g., alpha_brief, alpha_search) that serve different analytical purposes.

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?

Description provides clear context for when to use: for price/funding condition triggers. It does not explicitly mention alternatives or when not to use, but sibling context makes differentiation easy.

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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