Proof Holdings

verify_2fa

Submit a verification code to complete a 2FA challenge. Rate limited to 10 attempts per minute.

ACCESS: needs a Proof account. Authenticate this client (Claude Code: /mcp → Authenticate), or sign in with start_login — a session opens this tool — then call this tool again.

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": {
      "session_id": "<session_id>",
      "code": "<code>"
    },
    "name": "verify_2fa"
  }
}

Input Schema

Name	Required	Description	Default
`code`	Yes	Verification code
`session_id`	Yes	2FA session ID

Output Schema

Name	Required	Description
`status`	Yes
`verified_at`	Yes
`grant_expires_at`	Yes	When the grant this step-up stored stops being accepted
`grant_single_use`	Yes	Whether the grant is spent by the first act it allows

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedNov 2, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": {},
+  "description": "The step-up is complete and its grant stored",
+  "properties": {
+    "grant_expires_at": {
+      "description": "When the grant this step-up stored stops being accepted",
+      "type": "string"
+    },
+    "grant_single_use": {
+      "description": "Whether the grant is spent by the first act it allows",
+      "type": "boolean"
+    },
+    "status": {
+      "type": "string"
+    },
+    "verified_at": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "status",
+    "verified_at",
+    "grant_expires_at",
+    "grant_single_use"
+  ],
+  "type": "object"
+}

Changed1 schema field changedOct 26, 2026
- removedInput schema / additionalProperties
```
Removed value: -false
```
First observedSep 19, 2026

TDQS

A3.7/5.0

Behavior4/5

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

The description discloses two things that annotations do not: a rate limit of 10 attempts per minute and a Proof-account authentication prerequisite. The annotations only say this is not read-only and not destructive. It does not say what happens on a wrong or expired code, such as session invalidation or attempt counting.

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

Conciseness4/5

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

The purpose and rate limit are front-loaded in one tight sentence, which is good. The ACCESS paragraph earns its place by explaining authentication, but the phrasing 'a session opens this tool' is muddled and costs some clarity.

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?

This is a two-parameter mutation with an output schema, so return values need no explanation. Authentication and throttling are covered. The remaining gap is failure behavior and the relationship to the sibling wait/verify tools.

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 coverage is 100%: session_id is documented as the 2FA session ID and code as the verification code, with length bounds. The description adds no format hints, such as whether the code is numeric or the code's lifetime. This is the usual baseline 3 when the schema does the work.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description gives a specific verb and resource: submitting a verification code to complete a 2FA challenge. That is clear enough to call the tool correctly. It does not, however, distinguish it from close siblings such as submit_verification_code, verify_2fa_magic_link or wait_for_2fa, so an agent must infer that this is the code-based 2FA step.

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?

Usage is implied rather than stated: the tool is used during a 2FA challenge, after a session exists from start_login/start_2fa. No alternative is named, so the boundary with submit_verification_code and wait_for_2fa is left to the agent. The credentials block is onboarding guidance, not a when-to-use rule.

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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