Borrowing it
Nothing to install: this file belongs to managedcode/PrompterOne. Take a copy, put it at the same path in your own repository, and replace the rules that are about this project with yours.
curl -O https://raw.githubusercontent.com/managedcode/PrompterOne/main/.codex/skills/dotnet-managedcode-mimetypes/SKILL.mdgit clone --depth 1 https://github.com/managedcode/PrompterOneWrote this? Show the measurements
A badge with what this costs and how it scanned, read live from this page, so it follows the numbers instead of freezing them. Markdown for a README, HTML for a documentation site or a project page.
[](https://agentmods.dev/skills/managedcode/prompterone/dotnet-managedcode-mimetypes)<a href="https://agentmods.dev/skills/managedcode/prompterone/dotnet-managedcode-mimetypes"><img src="https://agentmods.dev/badge/skills/managedcode/prompterone/dotnet-managedcode-mimetypes/github.svg" alt="Measured on agentmods" height="20"></a>Or the 80×15 button, for a site that already has a row of RSS and ATOM ones. Only the verdict fits; the numbers stay here.
<a href="https://agentmods.dev/skills/managedcode/prompterone/dotnet-managedcode-mimetypes"><img src="https://agentmods.dev/badge/skills/managedcode/prompterone/dotnet-managedcode-mimetypes.svg" alt="Reviewed on agentmods" width="80" height="20"></a>What it costs to keep this loaded
Counted locally with the o200k_base tokenizer, which is exact for GPT models; Claude uses its own tokenizer and its counts differ. Treat this as one consistent yardstick across the catalogue rather than a bill. Prices are per million input tokens.
| Model | Per session | Once invoked |
|---|---|---|
| Fable 5.1 | $0.00041 | $0.00353 |
| Opus 5.5 | $0.00016 | $0.00141 |
| Sonnet 5.5 | $0.00008 | $0.00071 |
| Haiku 4.5 | $0.00004 | $0.00035 |
Grade A, and why
dotnet-managedcode-mimetypes scanned grade A with 0 findings against 26 rules in 11 categories — prompt injection, anti-refusal, data exfiltration, privilege escalation, supply chain, agent snooping, system-prompt leakage, SSRF and excessive agency — measured 1mo ago.
A static scan of the body, not an audit. Every finding is printed with the line that produced it so you can judge whether it matters here. A mod is markdown that instructs an agent; that is exactly why what it instructs is worth reading.
Nothing flagged
None of the 26 patterns this scan looks for appear in this file: no shell pipes, no recursive deletes, no credential paths, no hidden text, no instruction-override or anti-refusal phrasing, no agent-config snooping. That is not a guarantee, it is the absence of the things that are checkable.
Copies of this mod
1 near-identical copy found in the catalogue:
- dotnet-managedcode-mimetypes — 95% identical, 2 lines differ
What it actually says
ManagedCode.MimeTypes
Trigger On
- integrating
ManagedCode.MimeTypesinto upload or download flows - mapping file extensions to content types in APIs or background processing
- reviewing content-type handling for files, blobs, or attachments
- documenting a reusable MIME-type decision point in a .NET application
Workflow
- Identify where the application needs stable MIME-type decisions:
- upload validation
- download response headers
- storage metadata
- attachment processing
- Centralize content-type mapping instead of scattering ad-hoc string tables across the codebase.
- Use one library boundary for extension and MIME lookups.
- Validate the extensions and media types that matter to the product.
- Document any product-specific overrides separately from the library defaults.
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"]
Deliver
- guidance on where MIME lookup belongs in application code
- recommendations for centralized content-type decisions
- validation expectations for real file types used by the product
Validate
- MIME mapping is not duplicated across multiple services or controllers
- important file types are verified explicitly
- response or storage code uses the resolved type consistently
What ships with it
1 file beside SKILL.md in the same directory: the scripts, references and assets a skill reads on demand. Not counted in the per-session cost; read them before you install if any of them is executable.
What this file has done since we first saw it
Hashed on every crawl. A supply-chain change to an agent config is a question of when, not whether, so the history is kept rather than the latest state alone.
- 1mo ago First seen · 46 lines · 41 tokens per session scan A 714532b202d9
dotnet-managedcode-mimetypes is a skill published in the GitHub repository managedcode/PrompterOne (45 stars, last pushed 5mo ago), licensed MIT. It adds 41 tokens to every session and 353 once invoked, about $0.0002 per session on Opus 5.5. A static security scan graded it A with 0 findings. No closer match exists in the catalogue, so it is treated as the original; first seen 2026-08-30.
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