FlagForge MCP Server

upload_artifact

Upload screenshots, pcaps, or notes to a CTF challenge as artifacts and get an ID to embed them in markdown writeups.

Instructions

Upload a file (screenshot, pcap, note) to a challenge as an artifact.

Provide either a local file path (read from disk) or raw content bytes with a filename. Returns the artifact record — use its id to embed images in writeups: alt text

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": {
      "challenge_id": "<challenge_id>"
    },
    "name": "upload_artifact"
  }
}

Input Schema

Name	Required	Description	Default
`filename`	No
`file_path`	No
`mime_type`	No
`challenge_id`	Yes
`content_base64`	No

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Sep 5, 2026

TDQS

A4.2/5.0

Behavior4/5

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

With no annotations, the description carries the behavioral burden. It discloses the operation, the input modes, the returned artifact record, and the practical use of its id for embedding images in writeups. It does not cover permissions, size limits, or overwrite behavior, but the core behavior is transparent.

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 compact, front-loaded with the core purpose, and every sentence adds either usage or output context. The embed example is directly actionable without adding unnecessary length.

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?

For a 5-parameter tool with no output schema and no annotations, the description covers the main workflow, return value, and a concrete downstream use. It is not fully exhaustive because mime_type and encoding details are left implicit, but it is sufficiently complete for an agent to call it correctly in most cases.

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 0%, so the description must compensate. It usefully explains the file_path vs. content_base64 distinction and the role of filename, but it does not mention mime_type or clarify that 'raw content bytes' should be base64-encoded as content_base64 implies. This leaves some parameter ambiguity.

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 names a specific verb ('Upload'), a target resource ('a challenge as an artifact'), and gives concrete examples of accepted file types. This clearly distinguishes it from siblings like list_artifacts or save_evidence.

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?

It gives clear context: upload an artifact to a challenge, and provides two mutually exclusive input methods (local file path vs. raw content bytes with a filename). It does not explicitly name sibling alternatives or state when not to use the tool, so it stops short of a 5.

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