Hermes Plant

Start checkout

start_checkout

Start a Stripe checkout session for a product slug

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": {
      "slug": "<slug>"
    },
    "name": "start_checkout"
  }
}

Input Schema

Name	Required	Description	Default
`slug`	Yes	Product slug to purchase

Output Schema

Name	Required	Description
`ok`	Yes	True when the upstream storefront call returned a 2xx response
`httpStatus`	Yes	Upstream HTTP status code
`paymentRequired`	No	True when the response is an x402 HTTP 402 payment challenge

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedJul 9, 2026
- removedInput schema / additionalProperties
```
Removed value: -false
```
Changed1 schema field changedJul 9, 2026
- addedInput schema / additionalProperties
```
Added value: +false
```
Changed1 schema field changedJul 4, 2026
- removedInput schema / additionalProperties
```
Removed value: -false
```
Changed1 schema field changedJul 2, 2026
- addedInput schema / additionalProperties
```
Added value: +false
```
Changed1 schema field changedJul 2, 2026
- removedInput schema / additionalProperties
```
Removed value: -false
```

Changed1 schema field changedJun 29, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "httpStatus": {
+      "description": "Upstream HTTP status code",
+      "type": "number"
+    },
+    "ok": {
+      "description": "True when the upstream storefront call returned a 2xx response",
+      "type": "boolean"
+    },
+    "paymentRequired": {
+      "description": "True when the response is an x402 HTTP 402 payment challenge",
+      "type": "boolean"
+    }
+  },
+  "required": [
+    "ok",
+    "httpStatus"
+  ],
+  "type": "object"
+}

First observedJun 23, 2026

TDQS

A3.6/5.0

Behavior2/5

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

Annotations already indicate this is a non-read-only, non-idempotent operation with potential open-world effects. The description adds no additional behavioral context (e.g., whether a charge occurs immediately, if a session URL is returned, or if the operation is reversible). It only restates the basic action.

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?

The description is a single, front-loaded sentence with no fluff or redundant wording. Every word adds meaning, making it highly concise and well-structured.

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?

Given the tool's low complexity (one required parameter, output schema present, annotations provided), the description covers the essential purpose. It does not detail return values or side effects, but the output schema exists and the context signals are sufficient for a simple checkout initiation tool.

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%: the slug parameter is documented as 'Product slug to purchase', and the tool description references 'product slug', reinforcing the same meaning. The description adds no new information beyond the schema, serving as a baseline adequate case.

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 uses a specific verb ('Start') with a clear resource ('Stripe checkout session') and a scoping parameter ('for a product slug'). It unambiguously identifies the tool's function and distinguishes it from siblings like get_checkout_policies or list_products.

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 core usage is implied: use when you want to start a checkout for a given product slug. However, there is no explicit guidance on when not to use this tool or how it compares to related payment tools like payment_policy_decide or purchase_with_x402, leaving room for ambiguity.

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

All Hermes Plant tools Inspect

Try in Browser

One endpoint for every MCP toolRayrun runs every MCP server behind one URL and holds the credentials. Each call is decided per client, tool, and argument, then recorded.ray.runAd

Glama MCP Gateway

Add one secure layer between your agents and this server.

Resources

Need Help?