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/ferrus-dev/ferrus/nevanpx skills add ferrus-dev/ferrus --skill nevagit clone --depth 1 https://github.com/ferrus-dev/ferrusWrote 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/ferrus-dev/ferrus/neva)<a href="https://agentmods.dev/skills/ferrus-dev/ferrus/neva"><img src="https://agentmods.dev/badge/skills/ferrus-dev/ferrus/neva.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 | $0.00094 | $0.02309 |
| Opus 5 | $0.00047 | $0.01154 |
| Sonnet 5 | $0.00019 | $0.00462 |
| Haiku 4.5 | $0.00009 | $0.00231 |
Grade A, and why
neva 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 — 211 lines — stays where its author put it; the contents beside it link to each section on GitHub.
neva — MCP servers and clients in Rust
neva is a Rust SDK for the Model Context Protocol. One crate covers both
sides: App builds servers, Client builds clients, and a single process
can run both.
This skill describes neva 0.5.x, which speaks MCP 2026-07-28 by
default. That protocol generation broke compatibility with everything
before it. Most MCP knowledge in circulation — and every other MCP SDK —
describes the older generation, so the failure mode here is not "you
forget an API", it is "you confidently write the previous protocol". The
Non-negotiables section below is the list of places
where that happens. Read it before writing code, every time.
Step 1 — establish the version and the profile
Do this first; it changes which API is correct.
cargo add neva --features server-full # server
cargo add neva --features client-full # client
cargo add neva --features full # both
In an existing project, read Cargo.toml:
| What you find | What it means |
|---|---|
neva = "0.5" and no legacy-spec |
Default profile, MCP 2026-07-28. This skill applies as written |
features = [… "legacy-spec" …] |
Legacy profile, MCP 2024-11-05 … 2025-11-25. A different API. Read references/legacy.md before touching anything |
neva = "0.4" or older |
Pre-2026-07-28 by default. Read references/legacy.md for the upgrade |
proto-2026-07-28-rc |
A flag that no longer exists — remove it |
legacy-spec is a switch, not an addition: it compiles the 2026-07-28
surface out. The two generations never coexist in one build. Because Cargo
features are additive, --all-features turns legacy-spec on and
therefore tests the legacy profile — use --features "server-full client-full" to exercise the default one.
Step 2 — route to the reference you need
Load only what the task calls for; each file is self-contained.
| The task | Read |
|---|---|
| Tools, prompts, resources, schemas, content types, completion | references/server.md |
| DI, middleware, logging, progress, subscriptions on the server | references/server.md |
| Connecting, calling tools, batching, subscribing, client handlers | references/client.md |
Asking the user for input mid-handler; input_required; re-run safety |
references/mrtr.md |
Long-running work, tasks/get polling |
references/mrtr.md |
| Transport choice, TLS, JWT/OAuth, DNS-rebinding, multi-instance deploy | references/http.md |
| A custom HTTP stack (axum, hyper, actix-web) | references/http.md |
An error code, a -320xx on the wire, or "why is this rejected" |
references/troubleshooting.md |
legacy-spec, MCP ≤ 2025-11-25, upgrading from 0.4.x |
references/legacy.md |
What ships with it
7 files 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.
- 2d ago First seen · 211 lines · 94 tokens per session scan A 11ea16a79be0
neva is a skill published in the GitHub repository ferrus-dev/ferrus (2 stars, last pushed yesterday), licensed Apache-2.0. It adds 94 tokens to every session and 2,309 once invoked, about $0.0005 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 2026-09-04.
Other skills, from other repositories
rust-check
Run cargo check on the current Rust project to find compile errors.
thread-outbox-provider-push
Publish a fixture thread outbox entry through the Rust thread-outbox-provider front.
Rust Standards
Complete Rust coding, linting, testing, architecture, and layer boundary standards for systemprompt.io development.
agentic-infrastructure-2026
Build and adopt production AI agent infrastructure in 2026. Covers framework selection (LangGraph, CrewAI, AutoGen, MCP), orchestration patterns, evaluation, observability, memory systems, and tool use. Also covers the SOCIAL dimension: how to sell agent infrastructure internally, change management, measuring ROI…
azure-keyvault-certificates-rust
Azure Key Vault Certificates SDK for Rust. Use for creating, importing, and managing certificates.
azure-keyvault-keys-rust
Azure Key Vault Keys SDK for Rust. Use for creating, managing, and using cryptographic keys. Triggers: "keyvault keys rust", "KeyClient rust", "create key rust", "encrypt rust", "sign rust".