Borrowing it
Nothing to install: this file belongs to fieldcure/fieldcure-mcp-essentials. 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/fieldcure/fieldcure-mcp-essentials/main/CLAUDE.mdgit clone --depth 1 https://github.com/fieldcure/fieldcure-mcp-essentialsWrote 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/instructions/fieldcure/fieldcure-mcp-essentials/claude-md)<a href="https://agentmods.dev/instructions/fieldcure/fieldcure-mcp-essentials/claude-md"><img src="https://agentmods.dev/badge/instructions/fieldcure/fieldcure-mcp-essentials/claude-md.svg" alt="Measured on agentmods" 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 | $0.01096 | $0.01096 |
| Opus 5 | $0.00548 | $0.00548 |
| Sonnet 5 | $0.00219 | $0.00219 |
| Haiku 4.5 | $0.00110 | $0.00110 |
Grade A, and why
fieldcure-mcp-essentials CLAUDE.md 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 7d 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.
How it starts
The opening of the file, as written. The whole thing — 57 lines — stays where its author put it; the contents beside it link to each section on GitHub.
FieldCure.Mcp.Essentials
Cross-platform .NET 8 MCP server. Tools live in src/FieldCure.Mcp.Essentials/Tools/*.cs, packaged as NuGet FieldCure.Mcp.Essentials and distributed via dnx.
Tool authoring conventions
- Tools are static methods on a
[McpServerToolType]class with[McpServerTool(Name = "snake_case", Destructive = true|false)]and a prescriptive[Description]. - Parameter names use snake_case (
working_directory,max_output_chars) — they reach the LLM verbatim through the schema. - Always return
JsonSerializer.Serialize(result, McpJson.Options).McpJson.OptionsappliesJsonNamingPolicy.SnakeCaseLower, so PascalCase anonymous types serialize as snake_case JSON automatically. - Errors return
{ "error": "<message>" }rather than throwing. - Tool/parameter descriptions are LLM-steering surface area: be prescriptive about when to use which option, not just what it is. Mirror the
HttpRequestToolmax_response_charsandRunCommandToolshelldescriptions.
RunCommandTool subtleties
These are non-obvious and easy to break:
cmd.exe(shell: "auto"on Windows,shell: "cmd") uses rawpsi.Arguments, notArgumentList. cmd does not parse argv with CommandLineToArgvW conventions, andArgumentListleaks backslashes around embedded quotes (echo "a"→\"a\"). All other shells useArgumentList.- PowerShell shells (
pwsh,powershell) use-EncodedCommandwith a UTF-8 prelude ($OutputEncoding=[Console]::OutputEncoding=[System.Text.Encoding]::UTF8;) prepended before base64 encoding. Without the prelude, Windows PowerShell 5.1 emits OEM-codepage bytes (CP949 on Korean Windows) and the parent's UTF-8 reader sees mojibake. - Output truncation must keep draining the pipe after the visible cap; breaking the read loop deadlocks verbose children on a full stdout/stderr pipe.
- The shell-availability cache stores successes only. Failures are re-probed so a transient cold-start miss (AV scan, slow disk) does not poison the rest of the process lifetime. Probe timeout is 5 s.
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.
- 7d ago First seen · 57 lines · 1,096 tokens per session scan A d3ac371c351b
fieldcure-mcp-essentials CLAUDE.md is an instructions file published in the GitHub repository fieldcure/fieldcure-mcp-essentials (0 stars, last pushed 3mo ago), licensed MIT. It adds 1,096 tokens to every session, about $0.0055 per session on Opus 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 2026-08-31.
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