Managedcode Mimetypes

What it does

When your agent uses it

• : integrating ManagedCode.MimeTypes into upload
• Mapping file extensions to content types in APIs
• Background processing
• Reviewing content-type

Example prompts

• “/managedcode-mimetypes”

Requirements

• Compatibility (from SKILL.md): Requires a .NET application that integrates ManagedCode.MimeTypes or evaluates MIME type mapping behavior.

Workflow steps

5 steps, taken from the first numbered list in SKILL.md.

1. 1Identify where the application needs stable MIME-type decisions
2. 2Centralize content-type mapping instead of scattering ad-hoc string tables across the codebase.
3. 3Use one library boundary for extension and MIME lookups.
4. 4Validate the extensions and media types that matter to the product.
5. 5Document any product-specific overrides separately from the library defaults.

What it can do on your machine

Read from SKILL.md and the folder at commit 535dd55. It shows what the files ask for, not the result of running them.

• Tool permissions

  Pre-approves nothing: there is no allowed-tools line, so your agent's usual permission prompts apply.

  From allowed-tools in the SKILL.md frontmatter.

• Runs code

  Shell commands in SKILL.md call:

  • dotnet

  From the folder's file list and the shell code blocks in SKILL.md.

• Network

  Links to these hosts (documentation or services it may open):

  • github.com

  From URLs in SKILL.md, links to its own repository left out.

• Credentials

  Names no API keys, tokens, secrets or passwords.

  From names ending in _API_KEY, _TOKEN, _SECRET, _KEY or _PASSWORD in SKILL.md.

• Compatibility

  Requires a .NET application that integrates ManagedCode.MimeTypes or evaluates MIME type mapping behavior.

  From compatibility in the SKILL.md frontmatter.

Context cost

Managedcode Mimetypes loads about 1.5k tokens when it runs. Until then it costs about 151 tokens; SKILL.md has 463 words of instructions outside code blocks.

Always · name and description, kept in context so the agent knows when to use it

~151

When it runs · the whole SKILL.md, loaded when a task matches

~1.5k

Estimates: characters ÷ 4, the usual rule of thumb; real counts depend on the model's tokenizer. Scripts and assets cost tokens only if the agent reads them.

Safety

Automated static check — not a guarantee. Review scripts before installing. It scans the text of SKILL.md for risky patterns (piping downloads into a shell, reading credential files, hidden Unicode, destructive commands); files beside SKILL.md are not scanned.

SKILL.md

The full file from managedcode/dotnet-skills at commit 535dd55, republished under its MIT licence (© managedcode). 463 words, ~1,473 tokens.

name

managedcode-mimetypes

description

Use ManagedCode.MimeTypes when a .NET application needs consistent MIME type detection, extension mapping, and content-type decisions for uploads, downloads, or HTTP responses. USE FOR: integrating ManagedCode.MimeTypes into upload or download flows; mapping file extensions to content types in APIs or background processing; reviewing content-type. DO NOT USE FOR: unrelated stacks; generic tasks that do not need this specific guidance. INVOKES: inspect the repository context, edit targeted files, and run relevant build, test, lint, or validation commands when changes are made.

compatibility

Requires a .NET application that integrates ManagedCode.MimeTypes or evaluates MIME type mapping behavior.

dotnet add package ManagedCode.MimeTypes --version 10.1.1

<PackageReference Include="ManagedCode.MimeTypes" Version="10.1.1" />

using ManagedCode.MimeTypes;

var reportType = MimeHelper.GetMimeType("report.pdf");
var archiveType = MimeHelper.GetMimeType("archive.tar.gz");
var imageType = MimeHelper.GetMimeType("https://cdn.example.test/avatar.png?v=2");
var jpegExtensions = MimeHelper.GetExtensions("image/jpeg");

if (MimeHelper.TryGetMimeTypeInfoByExtension("report.pdf", out var info))
{
    Console.WriteLine($"{info.Mime} registered={info.IsIanaRegistered}");
}

MimeHelper.RegisterMimeType("acme", "application/x-acme");
var customType = MimeHelper.GetMimeType("invoice.acme");

MimeHelper.UnregisterMimeType("acme");

using var stream = upload.OpenReadStream();

if (!MimeHelper.MatchesMimeTypeByContent(stream, upload.ContentType) ||
    !MimeHelper.MatchesExtensionByContent(upload.FileName, stream))
{
    throw new InvalidOperationException("Upload content does not match its declared type.");
}

flowchart LR
  A["File name or extension"] --> B["ManagedCode.MimeTypes lookup"]
  B --> C["Resolved MIME type"]
  C --> D["Upload validation, storage metadata, or HTTP response"]

© managedcode, MIT. Rendered from Markdown: HTML in the file is shown as text, images as links, and headings moved down two levels. Raw file

Files

SKILL.md and 1 other file in catalog/Libraries/ManagedCode-MimeTypes/skills/managedcode-mimetypes of managedcode/dotnet-skills.

• SKILL.md
• manifest.json

Open the folder on GitHubat commit 535dd55