FactReason

Create a top-up link

factreason_create_topup_link

Create a Stripe Checkout URL for adding prepaid credit to the calling Bearer API key. This creates an external checkout session but does not charge a card. You CANNOT COMPLETE THE PAYMENT YOURSELF, so return the URL to a human, and credit is applied only after they complete payment. Use after HTTP 402 or when balance is low; the tool itself is not metered.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`apiKey`	No	Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.
`amountUsd`	Yes	Credit amount in USD; common blocks are 10, 50, and 200

Output Schema

TableJSON Schema

Name	Required	Description	Default
`error`	No
`created`	No
`amountUsd`	No
`balanceUrl`	No
`checkoutUrl`	No
`createKeyUrl`	No
`instructions`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedOct 4, 2026

addedInput schema / properties / apiKey

Added value: +{
+  "description": "Your FactReason API key, from factreason_create_key. Pass it here when your MCP client cannot set the Authorization: Bearer header on this connection; if the header is set, omit this. Never pass a key that belongs to someone else.",
+  "maxLength": 128,
+  "minLength": 1,
+  "type": "string"
+}

Changed5 schema fields changedAug 14, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

changedInput schema / properties / amountUsd / description

Previous value: -"Amount of credit to purchase in USD, between 1 and 1000. Common blocks: 10, 50, 200."New value: +"Credit amount in USD; common blocks are 10, 50, and 200"

addedInput schema / properties / amountUsd / maximum
```
Added value: +1000
```
addedInput schema / properties / amountUsd / minimum
```
Added value: +1
```

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": true,
+  "properties": {
+    "amountUsd": {
+      "type": "number"
+    },
+    "balanceUrl": {
+      "format": "uri",
+      "type": "string"
+    },
+    "checkoutUrl": {
+      "format": "uri",
+      "type": "string"
+    },
+    "createKeyUrl": {
+      "format": "uri",
+      "type": "string"
+    },
+    "created": {
+      "type": "boolean"
+    },
+    "error": {
+      "type": "string"
+    },
+    "instructions": {
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

First observedAug 14, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Goes well beyond the annotations: it discloses that an external checkout session is created but no card is charged, that payment cannot be completed by the agent, that credit is only applied after a human pays, and that the tool itself is not metered. This is exactly the extra behavioral context annotations cannot convey.

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?

Four tight sentences with the core action front-loaded followed by the critical human-handoff constraint and the usage trigger. No sentence is filler.

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

Completeness5/5

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

An output schema exists, so return-value explanation is unnecessary; the description instead covers the payment lifecycle and the agent's limitation. Nothing an agent needs to call this safely and correctly is absent.

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%, so both parameters (apiKey, amountUsd) are already fully documented in the schema, including the key-omission guidance. The description adds only the framing that the key is 'the calling Bearer API key', which is marginal; baseline 3 applies.

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?

States a specific verb and resource ('Create a Stripe Checkout URL for adding prepaid credit') and scopes it to the calling Bearer API key. No sibling tool overlaps with this purpose, so an agent can distinguish it immediately.

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

Usage Guidelines5/5

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

Gives an explicit trigger ('Use after HTTP 402 or when balance is low') and an explicit operational constraint ('You CANNOT COMPLETE THE PAYMENT YOURSELF, so return the URL to a human'). With no competing sibling, no alternative routing is needed.

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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