Detect MIME Type

file.detect_mime

ProductionBounded custom (Class B)Deterministicverifiablefastv1.0.0

File inputNo network

Overview

You give us a managed file reference and we detect its MIME type from content magic bytes, cross-check the filename extension and any declared content type you supply, and flag mismatches (for example a PNG named .txt). We read only a bounded prefix — we never fully parse or render the file. Do not use this when you need deep structural validation of a complex document.

Filenames lie — content-based detection is safer for routing and validation.

Reliability

The same bytes give the same answer on this deployment, though a Tika upgrade can refine a type or a confidence score, so treat the value as version-sensitive rather than frozen forever. A file reference resolves only inside your own tenant; if it has expired or was never yours, you get a validation error saying it is not accessible, and retrying will not change that — upload the file again and pass the new reference. A readLimitBytes outside 1 to 5,242,880 or a mode outside content_first, extension_first, and strict fails the same way, so fix the field and call again. A clean result says what the bytes look like; it never certifies that a file is free of malware.

Context footprint

Returns mimeType, confidence, mismatch flags, optional warnings, and inspection metadata. A successful call costs 5 execution credits.

When to use it

Before you process or route an uploaded file based on its type.

When you need deep structural validation or malware scanning.

Scope

Note

Detects MIME type from a bounded content prefix with optional extension cross-check.

Non-goals

Does not fully parse or render files
Does not trust the filename extension alone in content_first mode
Does not validate archive structure or malware

Properties

IdempotentRetry safeStreaming supportedFile input supportedRequires external service

Capabilities

analysisparsing

Cost & billing

Flat rate per invocation

MetercallsBillable onsuccessCost per call5 credits

File handling

Accepts file_refProduces file_refMax input2 MBMax file size5 MB

File limits

Constraints this skill applies to your input and generated files. The “Limited by” column shows the static source of each cap; none of these can be raised by upgrading your plan.

Limit	Value	Limited by
Maximum size per input file	5 MiB	Skill and platform maximum

How we handle your data

Protected temp storage

What this means

This skill may temporarily store files or intermediate data only to complete execution. Temporary data is protected and automatically deleted.

Squillify guarantees

Runs inside Squillify
This skill runs inside Squillify.
Payloads are not sent to an external service by this skill.
Temporary execution only storage
Squillify does not permanently store submitted payloads.
Telemetry records metadata only, not submitted content.
Submitted payloads are not used for training.
Submitted payloads are not reviewed by humans.
This skill does not target sensitive data.
The response may contain submitted or transformed content.

Your responsibility

Squillify does not determine whether submitted content is sensitive. Your application is responsible for deciding what data it is allowed to submit. Your application is responsible for securing the response.

Read the Microskill Data Handling Policy

Input schema

Field	Type	Required	Description
fileRef	string	Yes	Managed file reference resolved inside the current tenant.
filename	string	No	Original filename used for extension hinting; omit it to skip the extension cross-check.
declaredContentType	string	No	Content type the client claims; omit it to skip that comparison.
readLimitBytes	integer	No	Maximum prefix bytes to inspect; omit it for 1048576.
mode	string	No	How content and extension are combined; omit it for content_first.

Output schema

Field	Type	Required	Description
ok	boolean	Yes	Always true on success.
mimeType	string	Yes	Resolved MIME type for the inspected prefix.
extensionMimeType	string	No	MIME type implied by filename; omitted when filename was not supplied.
declaredContentType	string	No	Echo of declaredContentType when supplied.
confidence	number	Yes	Detection confidence from 0 through 1.
mismatch	boolean	Yes	True when resolved type disagrees with extension or declared type.
warnings	array	No	Bounded array of 0 through 16 plain-text advisories, where each item is one non-fatal warning string.
metadata	object	No	Closed detection metadata naming bytes inspected, mode, and engine.

API contract

POST /v1/execute

curl

curl -sS -X POST "$BASE/v1/execute" -H "Authorization: Bearer $KEY" -H 'Content-Type: application/json' -d '{"skillKey":"file.detect_mime","input":{"fileRef":"squillify://files/f-1","filename":"report.pdf"}}'

Integrations

TypeScript SDK

import { Squillify } from "@squillify/sdk";

const sq = new Squillify({ apiKey: process.env.SQUILLIFY_API_KEY });

const { output } = await sq.execute("file.detect_mime", {"fileRef":"squillify://files/f-1","filename":"logo.txt"});

Errors

Code	HTTP	Retryable	Description
VALIDATION_ERROR	400	No	The request payload failed schema validation.
UNAUTHORIZED	401	No	Missing or invalid API key.
SKILL_NOT_ACCESSIBLE	403	No	The API key is not granted access to this skill.
SKILL_NOT_AVAILABLE_FOR_PLAN	403	No	This skill is not included in your current plan.
PLAN_ELIGIBILITY_UNAVAILABLE	503	Yes	Plan eligibility could not be decided. Retry after backoff.
SKILL_NOT_FOUND	404	No	The requested skill or version does not exist.
TENANT_RATE_LIMITED	429	Yes	Request rate limit exceeded. Retry after backoff.
QUOTA_EXCEEDED	429	Yes	Plan quota exhausted. Retryable once the quota period resets.
EXECUTION_TIMEOUT	504	Yes	Execution exceeded the allowed time budget.

Other limits

Limit	Value
Recommended inline bytes	32 KiB

Limitations

Does not fully parse or render files
Does not trust the filename extension alone in content_first mode
Does not validate archive structure or malware
Deep PDF, Office, or media structural validation
Malware scanning or archive safety checks

How to call

POST /v1/execute (requires authentication)

Request bodyjson

{
  "skillKey": "file.detect_mime",
  "input": {
    "fileRef": "squillify://files/f-1",
    "filename": "logo.txt"
  }
}

Examples

PNG bytes with a .txt filename — mismatch flagged

Inputjson

{
  "fileRef": "squillify://files/f-1",
  "filename": "logo.txt"
}

Expected outputjson

{
  "confidence": 0.95,
  "ok": true,
  "mimeType": "image/png",
  "mismatch": true,
  "metadata": {
    "detectionMode": "content_first",
    "bytesInspected": 8,
    "engine": "tika-core"
  },
  "extensionMimeType": "text/plain"
}

JSON detected from content without a filename hint