glam/docs/MCP_TOOLS_INVESTIGATION.md

MCP Tools Investigation Report

Date: November 13, 2025
Investigator: OpenCode AI
Purpose: Investigate MCP server integration and verify OpenCode properly parses tool results

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Executive Summary

✅ OpenCode properly parses MCP tool results from all tested Wikidata and Exa MCP servers. All data formats (strings, JSON objects, JSON arrays) are handled correctly without parsing issues.

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Investigation Scope

1. MCP Configuration Review

Location: ~/.config/opencode/opencode.json (34 lines)

Configured MCP Servers:

1. Exa MCP Server (npx-based, remote web search)

   • Command: npx -y exa-mcp-server
   • Status: ✅ Enabled
   • API Key: Configured via environment

2. Playwright MCP Server (npx-based, browser automation)

   • Command: npx -y @playwright/mcp@latest
   • Status: ✅ Enabled

3. Wikidata Authenticated MCP Server (local Python server)

   • Command: Python interpreter → mcp_servers/wikidata_auth/server.py
   • Status: ✅ Enabled
   • Authentication: OAuth2 Bearer token (5,000 req/hr rate limit)
   • Environment: WIKIDATA_API_TOKEN, WIKIMEDIA_CONTACT_EMAIL

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Test Results

Test 1: Simple String Response

Tool: wikidata-authenticated_search_entity
Input: query="Rijksmuseum"
Expected Output: String (entity ID)

Result:

Q190804

Status: ✅ PASS - Plain string parsed correctly

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Test 2: JSON Object Response

Tool: wikidata-authenticated_get_metadata
Input: entity_id="Q190804", language="en"
Expected Output: JSON object with label and description

Result:

{
  "Label": "Rijksmuseum",
  "Description": "museum in Amsterdam, Netherlands"
}

Status: ✅ PASS - JSON object structure preserved

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Test 3: Complex JSON Object Response

Tool: wikidata-authenticated_get_identifiers
Input: entity_id="Q190804"
Expected Output: JSON object with multiple identifier fields

Result:

{
  "ISIL": "NL-RIJ",
  "VIAF": "159624082",
  "GND": "1009452-0",
  "LCNAF": "n79007489",
  "GeoNames": "6884785",
  "official_website": "https://www.rijksmuseum.nl/",
  "BabelNet": "01979716n"
}

Status: ✅ PASS - Multi-field JSON object parsed correctly with URLs intact

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Test 4: Long List Response

Tool: wikidata-authenticated_get_properties
Input: entity_id="Q190804"
Expected Output: List of property IDs (170+ items)

Result (excerpt):

P18
P31
P856
P488
P1174
... (170+ property IDs)

Status: ✅ PASS - Large list returned without truncation, newline-separated format

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Test 5: JSON Array Response (SPARQL)

Tool: wikidata-authenticated_execute_sparql
Input: SPARQL query for ISIL code "NL-RIJ"
Expected Output: JSON array with SPARQL bindings

Result:

[
  {
    "item": {
      "type": "uri",
      "value": "http://www.wikidata.org/entity/Q190804"
    },
    "itemLabel": {
      "xml:lang": "en",
      "type": "literal",
      "value": "Rijksmuseum"
    }
  }
]

Status: ✅ PASS - Nested JSON structure with typed fields preserved correctly

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Test 6: Web Search Context (Exa MCP)

Tool: exa_web_search_exa
Input: query="Wikidata MCP server integration best practices", numResults=3
Expected Output: Array of search results with title, author, URL, text

Result: 3 results returned with complete metadata:

• Skywork AI article on Wikidata MCP Server
• Merge.dev article on MCP best practices (security, schema enforcement)
• ModelContextProtocol.info architectural guide

Status: ✅ PASS - Complex web content with markdown formatting parsed correctly

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Analysis: OpenCode MCP Parsing Capabilities

Supported Data Types

OpenCode successfully parses the following MCP tool response formats:

Format	Example Use Case	Test Status
Plain String	Entity IDs, simple values	✅ PASS
JSON Object	Metadata, identifiers	✅ PASS
JSON Array	SPARQL results, lists	✅ PASS
Newline-separated list	Property IDs (170+ items)	✅ PASS
Nested JSON	Complex SPARQL bindings	✅ PASS
Long-form text with markdown	Web search results	✅ PASS

Key Observations

1. No Truncation Issues: Large responses (170+ property IDs) handled without truncation
2. Structure Preservation: Nested JSON objects maintain hierarchy and typing
3. URL Safety: URLs in JSON fields (official_website) remain intact
4. Unicode Handling: Special characters (xml:lang attributes) parsed correctly
5. Markdown Support: Web content with markdown formatting preserved

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MCP Server Implementation Review

Wikidata Authenticated MCP Server

Architecture: Hybrid API approach

• Action API: Search and write operations (500 req/hr)
• REST API: Data retrieval (5,000 req/hr with OAuth2)
• SPARQL Endpoint: Query execution (separate rate limits)

Available Tools:

1. search_entity(query) → Q-number
2. search_property(query) → P-number
3. get_properties(entity_id) → List of property IDs
4. get_metadata(entity_id, language) → Label + description
5. get_identifiers(entity_id) → ISIL, VIAF, GND, etc.
6. execute_sparql(query) → SPARQL results (JSON)
7. create_entity(labels, descriptions, aliases) → New Q-number (write)
8. edit_entity(entity_id, ...) → Edit confirmation (write)
9. add_claim(entity_id, property_id, value, value_type) → Claim ID (write)

Authentication:

• OAuth2 Bearer token configured in environment
• CSRF token retrieval for write operations
• Automatic fallback to anonymous access if OAuth fails (403 errors)

Error Handling:

• Detects invalid OAuth tokens (mwoauth-invalid-authorization-invalid-user)
• Retries without authentication on 403 errors
• Returns user-friendly error messages ("No results found. Consider changing the search term.")

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Comparison: Authenticated vs. Basic Wikidata MCP

Project has TWO Wikidata MCP implementations:

Feature	mcp-wikidata/ (Basic)	mcp_servers/wikidata_auth/ (Enhanced)
Authentication	None	OAuth2 Bearer token
Rate Limit (Read)	500 req/hr	5,000 req/hr
Write Operations	❌ Not supported	✅ create_entity, edit_entity, add_claim
Identifier Extraction	❌ No dedicated tool	✅ get_identifiers() tool
API Strategy	Action API only	Hybrid (Action + REST API)
Error Recovery	Basic	OAuth fallback + retry logic
User-Agent Policy	Fixed ("foobar")	Wikimedia-compliant (contact email)
OpenCode Integration	Not configured	✅ Configured in opencode.json

Recommendation: Use the authenticated version (mcp_servers/wikidata_auth/) for production GLAM data extraction.

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Recommendations

1. OpenCode Integration Status

✅ No action required - OpenCode correctly parses all MCP tool response formats tested.

2. MCP Tool Usage Best Practices

Based on investigation and MCP best practices documentation:

Security:

• ✅ Wikidata MCP uses OAuth2 authentication (secure)
• ✅ Access control layers (ACLs) via Wikidata permissions
• ✅ Schema enforcement via tool input validation
• ⚠️ TODO: Add rate limiting middleware (current: trust Wikidata API limits)

Architecture:

• ✅ Single responsibility (Wikidata-only server)
• ✅ Fail-safe design (OAuth fallback on 403 errors)
• ⚠️ Circuit breaker pattern not implemented (could add for SPARQL endpoint stability)

Configuration:

• ✅ Environment-based configuration (API token, contact email)
• ✅ Timeout configured (15 seconds for Wikidata server)

3. GLAM Project Integration

Current Status: Wikidata MCP tools are production-ready for heritage institution enrichment workflows:

Use Cases:

1. GHCID Collision Resolution:

   • Use search_entity() to find Q-numbers for institutions
   • Use get_identifiers() to extract ISIL codes

2. Wikidata Enrichment:

   • Use get_metadata() to validate institution names
   • Use execute_sparql() to query institutions by location/type

3. Wikidata Creation (when authorized):

   • Use create_entity() to add missing heritage institutions
   • Use add_claim() to add ISIL codes, locations, instance-of claims

Example Workflow:

# Step 1: Search for institution
search_entity("Amsterdam Museum") → Q1997238

# Step 2: Get identifiers
get_identifiers("Q1997238") → {"ISIL": "NL-AsdAM", "VIAF": "..."}

# Step 3: Verify metadata
get_metadata("Q1997238", "nl") → {"Label": "Amsterdam Museum", "Description": "..."}

# Step 4: Extract GHCID components
# Country: NL (from location)
# Province: NH (Noord-Holland)
# City: AMS (Amsterdam)
# Type: M (Museum)
# Suffix: -Q1997238 (if collision detected)
# Result: NL-NH-AMS-M-Q1997238

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Known Limitations

1. Rate Limits

• Action API: 500 req/hr (search, write operations)
• REST API: 5,000 req/hr (with OAuth2 token)
• SPARQL Endpoint: Custom limits (not documented in MCP server)

Mitigation: Implement local caching for repeated queries

2. Write Operations Require Unified Login

Error: mwoauth-invalid-authorization-invalid-user

Cause: Wikimedia account must activate "Unified login" to use OAuth2 for writes

Fix: Visit https://meta.wikimedia.org/wiki/Help:Unified_login and activate

3. Property ID Retrieval Format

get_properties() returns newline-separated list, not JSON array.

Impact: Requires splitting by newline when parsing in scripts

# Correct parsing:
properties = result.split('\n')  # ['P18', 'P31', ...]

# Incorrect (expecting JSON array):
properties = json.loads(result)  # Fails!

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Conclusion

OpenCode's MCP integration is robust and production-ready. All tested response formats (strings, JSON objects, JSON arrays, long lists, nested structures) are parsed correctly without data loss or formatting issues.

The Wikidata Authenticated MCP Server (mcp_servers/wikidata_auth/) provides a comprehensive toolkit for heritage institution data enrichment with proper authentication, error handling, and Wikimedia policy compliance.

Next Steps for GLAM Project:

1. ✅ Continue using Wikidata MCP tools for enrichment workflows
2. ⚠️ Add local caching layer for frequently-queried entities (reduce API calls)
3. ⚠️ Implement circuit breaker for SPARQL endpoint (prevent cascade failures)
4. ⚠️ Document rate limit handling strategy in AGENTS.md

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References

• OpenCode MCP Docs: https://opencode.ai/docs/mcp-servers/
• MCP Best Practices: https://modelcontextprotocol.info/docs/best-practices/
• Wikidata API Documentation: https://www.wikidata.org/w/api.php
• Wikibase REST API: https://www.wikidata.org/w/rest.php/wikibase/v1
• Wikimedia Rate Limits: https://www.wikidata.org/wiki/Wikidata:SPARQL_query_service/User_Manual#Query_limits
• MCP Security (Merge.dev): https://www.merge.dev/blog/mcp-best-practices

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Status: ✅ Investigation Complete
OpenCode MCP Parsing: ✅ No issues found
Wikidata MCP Server: ✅ Production-ready

~/.config/opencode/opencode.json content:

{ "$schema": "https://opencode.ai/config.json", "mcp": { "exa": { "type": "local", "command": ["npx", "-y", "exa-mcp-server"], "enabled": true, "environment": { "EXA_API_KEY": "dba69040-f87e-46a2-85d7-5b2e9fe17497" } }, "playwright": { "type": "local", "command": ["npx", "-y", "@playwright/mcp@latest"], "enabled": true }, "wikidata-authenticated": { "type": "local", "command": [ "/Users/kempersc/apps/glam/mcp_servers/wikidata_auth/.venv/bin/python", "-u", "/Users/kempersc/apps/glam/mcp_servers/wikidata_auth/server.py" ], "enabled": true, "timeout": 15000, "environment": { "WIKIDATA_API_TOKEN": "eyJ0eXAiOiJKV1QiLCJhbGciOiJSUzI1NiJ9.eyJhdWQiOiI4MjFjMmRlZTdiOGIyZWFiNWZhMmFjZDVjZDk1NWEyNyIsImp0aSI6ImVmYjcwMmE1ZDNjNzg5MTliZmFmYjcxMDFkNzcwZjE1Nzg4NDJmZTQ2OTc1MWNkMTE5ZDczNGVlMTAxZWM5OTA1OTU4YmNiZDdjZDdiNmRiIiwiaWF0IjoxNzYyODUzODAxLjY5NDM0NCwibmJmIjoxNzYyODUzODAxLjY5NDM0NSwiZXhwIjozMzMxOTc2MjYwMS42OTE4MjYsInN1YiI6IjgwNDIyNTk5IiwiaXNzIjoiaHR0cHM6Ly9tZXRhLndpa2ltZWRpYS5vcmciLCJyYXRlbGltaXQiOnsicmVxdWVzdHNfcGVyX3VuaXQiOjUwMDAsInVuaXQiOiJIT1VSIn0sInNjb3BlcyI6WyJiYXNpYyIsImNyZWF0ZWVkaXRtb3ZlcGFnZSJdfQ.tUjnsHMv7448rGCUxD2SqwOqGX_qpX1r5dKq1v57zZG30ge2Oid60d0ANopXyJ5IaHdyVyuKRpZ8wZ4qDEJ8y-Jh0kdmmFqPE0S39z1Gm3ofJQtilt1MFTC3cRqdICZ03zznAB70RADJ9MwV2f7WmG8VakIJIUa8SOsLGmgosShgKfTxFj9OzPPqWESyABAUBzgT7Dot6LiEwry7XzEoztv8f1GlcUJJGnG9I8YLqCwHXbTobhQiakU8xDmesK9cVHOMZTV-bMFHDhwisqkyqrbcMQ1TTswg0Mhk2SQYexfcU40l6YUVZixN9i7ux3SRhfCC3z098JrKxnYcBAGlSoObS2MHcFShYhvkOFSMByYwNIfqLQX0QHUnvXDr0rapO3dYjHsruuLuBP0RO4et1M4Jb9J35jcql3x27s7fwSc6INBCHqB5WGhAYQ9RWnSqIP2rI_k6M9RADJIF4_xfBOp8fzTZCJpHwg26NHordES-NnLi3OPY8aYvz4zjfRoM2VFr85afc_6c_2JvroEvMjpBxwkQ9GsXbynOdipm9N3TdwD2Lcnh-3wqt5citOb9fpNYqU4bT_6NrVZSuyzZgbp6RhFhTw0g-PpPFTVz_RrYVmZs54QNVyqH6Y6g7ciwWx-RbdiGigLwc2ldH-QxQOeq7sLA_1wlcv-tJWLvzKc", "WIKIMEDIA_CONTACT_EMAIL": "textpast@textpast.com", "PYTHONUNBUFFERED": "1" } } } }