Getting it into your agent
One page per mod, every tool's command on it. A separate URL per tool would split the same page into five that compete with each other.
npx agentmods add skills/leehack/mcp_dart/mcp-developernpx skills add leehack/mcp_dart --skill mcp-developergit clone --depth 1 https://github.com/leehack/mcp_dartWhat 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 | $0.00035 | $0.00672 |
| Opus 5 | $0.00017 | $0.00336 |
| Sonnet 5 | $0.00007 | $0.00134 |
| Haiku 4.5 | $0.00003 | $0.00067 |
Grade A, and why
mcp-developer 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 2d 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 — 41 lines — stays where its author put it; the contents beside it link to each section on GitHub.
MCP Developer
Use this skill when the work involves MCP protocol behavior, cross-SDK interop, server/client debugging, or host configuration.
Workflow
- Identify the transport first: stdio, Streamable HTTP, SSE, or a host-specific adapter.
- Preserve wire-level MCP semantics. Keep JSON-RPC ids, method names, capability flags, metadata, and error codes in their original spec-compatible shape.
- Check advertised capabilities before calling capability-specific methods.
- Reproduce with a protocol-level tool before editing app code:
mcp_dart inspect-server --json -- <server-command> ...- Configure a client/agent host to launch
mcp_dart inspect-client --report /tmp/mcp-client-report.json - Configure a client/agent host to launch
mcp_dart trace --report /tmp/mcp-trace.json -- <real-server-command> ... mcp_dart list-tools -- <server-command> ...mcp_dart call-tool <tool> --json-args '{"key":"value"}' -- <server-command> ...mcp_dart inspect --url http://localhost:3000/mcp
- Use
--probe-configwithinspect-serverwhen a server needs real tool arguments, resource URIs, prompt arguments, completion values, or task behavior. Keep destructive app actions out of default probes. - Treat
inspect-server,inspect-client, andtraceas the live debugging workflow. They return protocol checks or traffic evidence for real targets; there is no separate live validation command to prefer. - If changing this Dart SDK/CLI package itself, also run
mcp_dart conformance --suite all --jsonfor the built-in protocol regression fixtures. - For cross-language issues, test at least one non-Dart peer. Prefer the official TypeScript or Python MCP SDK when a reproduction can be made small, and use published servers such as filesystem/time when the bug depends on real package behavior.
- When changing protocol behavior, add regression coverage for the raw wire shape or interop edge case, not only a convenience API test.
Host Configuration Checks
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.
- 2d ago First seen · 41 lines · 35 tokens per session scan A b5aa26c4ba22
mcp-developer is a skill published in the GitHub repository leehack/mcp_dart (114 stars, last pushed 8d ago), licensed MIT. It adds 35 tokens to every session and 672 once invoked, about $0.0002 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 2026-08-30.
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