🤖 Percival Deep Research - percival.OS MCP

Version 3.0.0

📋 Description

Percival Deep Research is a highly capable MCP server designed to equip the Nanobot agent with autonomous, deep-dive web research capabilities. It explores and validates numerous sources, focusing only on relevant, trusted, and up-to-date information.

This server is part of the percival.OS ecosystem, a Personal Agentic Operating System designed for autonomy, security, and absolute privacy.

v3.0 highlights — 48 bugs closed across 4 official bug-hunt rounds and 2 internal code-reviews; surface expanded to 5 tools + 1 resource template + 4 prompts. Same single-endpoint inference model as v2.2.x. See CHANGELOG.md for the full history.

Related MCP server: perplexity-mcp-server

🛡️ percival.OS Principles

Like all components of percival.OS, this MCP server strictly follows our core principles:

• Privacy & Governance: The entire research and synthesis process is governed by your API keys and local configurations.

• Data Sovereignty: Knowledge extracted from the web is processed locally and integrated into your agent's context without external harvesting.

• Hardened Security: We implement Defense-in-depth with strict input sanitization against prompt injection and isolation of untrusted web content.

• Transparency: Based on the GPT Researcher project, but extensively refactored and hardened for the Percival ecosystem.

🚀 Surface (v3.0.0)

Tools (5)

Resource (1)

• research://{topic} — context direto (sem session). Percent-decode server-side.

Prompts (4) ✨ new in v3.0

⚙️ Configuration in percival.OS (Nanobot)

Quickstart (v3.0.0 — recommended)

The server uses a single inference endpoint (one LLM). Same setup works for any OpenAI-compatible gateway (OpenAI, Venice, MiniMax, OpenRouter, local LLMs, etc.):

{
  "mcpServers": {
    "percival-deep-research": {
      "command": "uv",
      "args": ["run", "--no-sync", "percival-deep-research"],
      "env": {
        "PYTHONUNBUFFERED": "1",
        "MCP_TRANSPORT": "stdio",
        "INFERENCE_API_KEY": "YOUR_KEY",
        "INFERENCE_BASE_URL": "https://api.minimax.io/v1",
        "INFERENCE_LLM": "minimax:MiniMax-M3",
        "RETRIEVER": "duckduckgo"
      },
      "tool_timeout": 300
    }
  }
}

⚠️ Use literals — INFERENCE_LLM=${INFERENCE_LLM:-default} e similares são template bash-style não-interpolados. v3.0 detecta isso e emite WARN, mas a pipeline quebra silenciosamente se não trocar. Em caso de dúvida, copie valor direto: INFERENCE_LLM=openai:gpt-4o-mini.

Migration from v2.x

- "OPENAI_API_KEY": "...",
- "OPENAI_BASE_URL": "https://api.venice.ai/api/v1",
- "FAST_LLM": "...",
- "SMART_LLM": "...",
- "STRATEGIC_LLM": "...",
- "EMBEDDING_LLM": "...",
- "PERCIVAL_LLM_PROVIDER_ALIASES": "venice:,minimax:,openrouter:",
- "BRAVE_API_KEY": "...",
+ "INFERENCE_API_KEY": "...",
+ "INFERENCE_BASE_URL": "...",
+ "INFERENCE_LLM": "<provider>:<model>",
+ "RETRIEVER": "duckduckgo"   // ou "brave" + BRAVE_API_KEY se quiser

Breaking changes v2.x → v3.0:

• ❌ OPENAI_* env vars (still accepted as fallback with deprecation log; will be removed in v4.0).

• ❌ FAST_LLM/SMART_LLM/STRATEGIC_LLM/EMBEDDING_LLM per-slot overrides (still honored when set, but INFERENCE_LLM is canonical).

• ❌ Llm-bridge expansion venice:, minimax:, openrouter: (now auto-detected from INFERENCE_BASE_URL).

• ❌ BRAVE_API_KEY is needed only if RETRIEVER=brave.

• ✅ v3.0 NEW: research_quick_brief, research_synthesis, research_health_diagnose prompts.

• ✅ v3.0 NEW: strict validation on deep_research(include_context) — accepts only real bool. 'yes'/'false'/1 are rejected at the framework level (Pydantic StrictBool in the type annotation).

⚠️ Known Limitations (v3.0.x)

These are honest design constraints, not bug reports:

1. Embeddings require an OpenAI-compatible provider. When you set INFERENCE_LLM=minimax:... (or venice:, openrouter:, etc.) for chat synthesis, the embedding slot is left unset instead of receiving the chat model — gpt-researcher/memory/embeddings.py previously received whatever INFERENCE_LLM said, which silently produced garbage. See troubleshooting below.

2. The four-slot override is gone if you skip INFERENCE_LLM. When you provide STRATEGIC_LLM/FAST_LLM/SMART_LLM/EMBEDDING_LLM but not INFERENCE_LLM, only the slots you explicitly set are honored. Workaround: set INFERENCE_LLM= to the chat-model you want everywhere.

3. gpt-researcher >= 0.16.0 upstream bug. The vendored copy in .venv (after uv sync) hits NameError: name 'Any' is not defined at import time. We've applied a from __future__ import annotations patch in our local venv (see scripts/patch_gpt_researcher.py). Without it, the server never boots. If you destroy your venv, re-run uv run python scripts/patch_gpt_researcher.py after uv sync.

4. DuckDuckGo retriever rate-limits on heavy traffic. DuckDuckGo doesn't publish rate limits but returns HTTP 429 after sustained scraping. Operators chaining large batched research should consider Brave (with BRAVE_API_KEY) or a local SearXNG instance.

5. include_context schema strictness (v3.0+). Pydantic StrictBool rejects 'yes', 'false', 1, 0, dict, etc. at the framework layer before the handler runs. Agents that previously passed 'yes'/'false' will see a ToolError. Fix: pass real True/False.

🛠️ Development & Testing

cd percival.OS_Dev
uv sync
uv run percival-deep-research

Test runs

# Whole suite (353 passed + 3 skipped; no integration deps needed).
uv run pytest -q

# Just the round 4+5 regression tests (placeholder detection, dedup, etc.).
uv run pytest tests/test_audit_round4_nano.py tests/test_audit_round5_placeholder.py -v

# Smoke test (boots, version prints):
INFERENCE_API_KEY=sk-fake INFERENCE_BASE_URL=https://api.minimax.io/v1 \
  INFERENCE_LLM=minimax:MiniMax-M3 \
  timeout 4 uv run --no-sync percival-deep-research

🛟 Troubleshooting (v3.0.x)

Error: Unsupported ${INFERENCE_LLM. (N0)

Cause: Your .env or config.json contains a bash-style placeholder template (${VAR} or ${VAR:-default}) that the loader could not interpolate. The literal string then hits gpt_researcher.config.config. parse_llm and produces a cryptic Unsupported ${INFERENCE_LLM..

v3.0 detection: If this happens, you'll also see this WARN at boot:

[S6] INFERENCE_LLM='${INFERENCE_LLM:-openai:gpt-4o-mini}' looks like an
UN-EXPANDED template placeholder. Most likely cause: `.env` or
`config.json` referenced a placeholder that the loader couldn't
interpolate.

Fix:

- INFERENCE_LLM=${INFERENCE_LLM:-openai:gpt-4o-mini}
+ INFERENCE_LLM=openai:gpt-4o-mini

Or in config.json:

- "INFERENCE_LLM": "${INFERENCE_LLM:-openai:gpt-4o-mini}"
+ "INFERENCE_LLM": "openai:gpt-4o-mini"

The same WARN [S6] fires on missing : in the value (e.g., INFERENCE_LLM=gpt-4o-mini) and on python-format %(...)s and on f-string {...} templates — all of these fail parse_llm the same way. The WARN points you to the exact file (.env or config.json).

"401 Incorrect API key" on custom gateway (B3, e.g. Venice, MiniMax)

Cause: gpt-researcher/memory/embeddings.py (upstream, not editable) reads os.environ["OPENAI_BASE_URL"] / os.environ["OPENAI_API_KEY"] directly. Setting only INFERENCE_BASE_URL / INFERENCE_API_KEY is insufficient — populate_inference_slots() in llm_bridge.py propagates these env vars to the legacy OPENAI_* namespace. To use on custom gateway:

INFERENCE_API_KEY=sk-your-gateway-key
INFERENCE_BASE_URL=https://api.venice.ai/api/v1
INFERENCE_LLM=venice:llama-3.3-70b

After startup, log line should show:

Inference provider: venice (auto-detected from INFERENCE_BASE_URL)

If it says openai, your INFERENCE_BASE_URL is wrong (must contain the gateway host — api.venice.ai, api.minimax.io, openrouter.ai).

pytest -q reports failures on a clean machine (B4)

Integration tests connect to localhost:8000 and fail if no server is up. v2.2.1+ adds an autouse fixture in tests/conftest.py that skips integration tests without a server:

uv run pytest -q
# Expected (v2.2.1+): N passed, M skipped

If you need to run them, start a server first:

# In one terminal:
MCP_TRANSPORT=sse uv run --no-sync percival-deep-research
# Then in another:
uv run pytest

__version__ reports the wrong number

Re-install the editable package:

uv pip install -e . --force-reinstall
# OR
uv sync

The regression test tests/test_audit_round3_nano.py::test_version_correto_no_runtime will fail loudly on any future drift.

research://topic with space fails with invalid domain character

FastMCP 3.4 Pydantic validator rejects non-ASCII in URI domains. v2.2.0+ added percent-decode server-side, so callers can either:

# Option A: percent-encode the topic (recommended)
await client.read_resource("research://S%C3%A3o%20Paulo")

# Option B: encode at the call site
import urllib.parse
uri = "research://" + urllib.parse.quote("São Paulo", safe="")
await client.read_resource(uri)

include_context='yes' returns ToolError (N8/N9)

This was v2.x lax-mode accepting string-coerced bool, v3.0+ enforces strict bool. Pass real True/False:

# Wrong (was accepted in <v3.0):
await client.call_tool("research_deep", {"query": "x", "include_context": "yes"})

# Right:
await client.call_tool("research_deep", {"query": "x", "include_context": True})

Affected: 'yes', 'false', 1, 0, {} and similar truthy/falsy non-bools. The framework (Pydantic StrictBool) now rejects these with a clear ToolError before our handler runs.

Spurious Future exception was never retrieved in server logs

Fixed in v3.0 (S3 fix): deep_research rate-limit-reject branch now calls future.exception() to consume the exception cleanly. If you still see this on a fork, ensure the in-flight dedup path consumes the exception:

if not future.done():
    future.set_exception(RuntimeError("..."))
future.exception()  # <- this line cleans the warning

Component already exists: template:research://{topic} at boot

Two triggers known in FastMCP 3.4:

1. Running server.py with python -i server.py (interactive mode imports modules twice).

2. Subprocess imports the package via importlib.reload().

The regression test tests/test_audit_round3_nano.py::test_apenas_um_template_research_topic catches this.

Boot emits [S6] WARN even though INFERENCE_LLM looks valid

Possible causes (after v3.0 review):

• A stray } character somewhere (e.g., model-v2}typo). v3.0 removed } as a false-positive signal, so this should not trigger anymore. If still triggered, file a bug.

• A leftover gpt-{name} template. v3.0 retains { as a placeholder signal — replace with literal values.

📚 About the Project

This server is an integral module of the percival.OS project. It enables Nanobot to perform complex research tasks that require multiple steps of validation and synthesis.

• Main Repository: https://github.com/bill-kopp-ai-dev/percival.OS

• License: MIT

📝 Versioning

See CHANGELOG.md for the complete history.

Developed with ❤️ by the percival.OS Team