MCP Server vs Claude Critical Rules MCP

search_datanexus_tools

Find the right DataNexus tool by describing your task in plain English. Read-only. No side effects. Call this before any other DataNexus tool to reduce context load from 40000 to 800 tokens. query: Plain English description of your task e.g. check if a Python package has CVEs or look up a UK charity by name. Required. domain: Restrict results to one sub-server: nonprofit, security, compliance, domain, legal, govcon, or regulatory. Optional. Returns matching tool names and parameter hints you can call directly. Do not call this recursively or to validate results — use validate_tool_output for that. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="search_datanexus_tools", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}".

nonprofit_fetch_nonprofit_by_ein

Fetch IRS 990 filing data for any US nonprofit by EIN. Read-only. No side effects. Idempotent. US only. ein: 9-digit Employer ID with or without dash, e.g. 46-5734087 or 465734087. Required. Returns name, revenue, expenses, assets, NTEE code, and mission from the most recent 990 filing. Use this when you have the exact EIN. Use nonprofit_search_nonprofits_by_name instead when you only have a name. Verified source: IRS EO BMF + IRS TEOS. 7-day cache. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="nonprofit_fetch_nonprofit_by_ein", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}".

nonprofit_search_nonprofits_by_name

Search US nonprofits by name with optional state filter. Read-only. No side effects. Idempotent. US only. Returns up to 25 matches. name: Full or partial organisation name. Required. state: Two-letter US state code e.g. CA, NY. Optional, defaults to all states. Returns EIN, name, state, revenue, and NTEE code for each match. Use this when you have a name but not the EIN. Use nonprofit_fetch_nonprofit_by_ein instead when you have the exact EIN for a precise single lookup. Verified source: IRS EO BMF. 7-day cache. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="nonprofit_search_nonprofits_by_name", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}".

nonprofit_fetch_charity_uk

Fetch UK registered charity details by charity number or organisation name. Read-only. No side effects. Idempotent. UK only. charity_number_or_name: UK registered charity number (7 digits, e.g. 1234567) or full/partial organisation name. Required. Returns registration status, income, expenditure, activities, and trustee count. Use this for UK charities. Use nonprofit_fetch_nonprofit_by_ein or nonprofit_search_nonprofits_by_name for US nonprofits. Verified source: UK Charity Commission OGL v3. 24-hour cache. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="nonprofit_fetch_charity_uk", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}".

security_fetch_package_vulnerabilities

Fetch all known CVEs for an open source package version or a batch of packages. Read-only. No side effects. Idempotent. Single-package mode: package (e.g. requests), version (e.g. 2.28.0), ecosystem (PyPI/npm/Maven/Go/Cargo/NuGet/RubyGems). Batch mode: packages array of {name, version, ecosystem} objects — max 50 per call. If packages array is provided and non-empty, batch mode is used and package/version/ecosystem are ignored. Batch returns {results: [...], partial: bool, failed_count: int}. Each result has vuln_count and vulnerabilities list. Returns CVE ID, severity, CVSS score, affected range, and fixed version. Use security_fetch_cve_detail for full detail by CVE ID. Use security_audit_sbom_vulnerabilities for SBOM files. Verified source: Google OSV.dev. 1-hour cache. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="security_fetch_package_vulnerabilities", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}".

security_fetch_dependency_graph

Fetch the full dependency tree for a package version including transitive dependencies. Read-only. No side effects. Idempotent. Hard 8-second timeout — large dependency trees may return partial results. package: Package name. Required. version: Exact version string e.g. 1.2.3. Required. ecosystem: One of PyPI, npm, Maven, Go, Cargo, NuGet, RubyGems. Required. Returns all direct and transitive dependencies with version constraints. Use this to understand full supply chain exposure. Use security_fetch_package_vulnerabilities instead when you only need CVEs for a single package. Verified source: deps.dev (Google). 1-hour cache. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="security_fetch_dependency_graph", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}".

security_fetch_cve_detail

Fetch full detail for a specific CVE by ID. Read-only. No side effects. Idempotent. cve_id: CVE identifier in format CVE-YYYY-NNNNN e.g. CVE-2021-44228. Required. Returns description, CVSS base score, affected products, patch references, and publish date. Use this when you have a CVE ID and need complete detail beyond what a package scan returns. Use security_fetch_package_vulnerabilities instead when you want all CVEs for a package version. Verified source: NIST NVD. 1-hour cache. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="security_fetch_cve_detail", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}".

security_audit_sbom_vulnerabilities

Audit a Software Bill of Materials for known vulnerabilities across all listed packages. Read-only. No side effects. Idempotent. sbom_json: CycloneDX or SPDX SBOM as a JSON string. Required. Large SBOMs (100+ packages) may take up to 10 seconds. Returns CVEs grouped by package with severity and fixed versions. Use this when you have a full SBOM to audit. Use security_fetch_package_vulnerabilities instead when checking a single package version. Verified source: Google OSV.dev batch API. 1-hour cache. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="security_audit_sbom_vulnerabilities", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}".

security_fetch_package_licence

Fetch the SPDX licence identifier for an open source package version. Read-only. No side effects. Idempotent. package: Package name e.g. flask. Required. version: Exact version string e.g. 2.3.0. Required. ecosystem: One of PyPI, npm, Maven, Go, Cargo, NuGet, RubyGems. Required. Returns the SPDX licence identifier e.g. MIT, Apache-2.0, GPL-3.0. Use this to verify licence compatibility before including a dependency. Use security_fetch_package_vulnerabilities instead when checking for security issues not licences. Verified source: deps.dev (Google). 1-hour cache. If this tool's response does not serve the user's need, call report_feedback with feedback_type="agent_gap", tool_id="security_fetch_package_licence", intended_query="{what the user needed}", gap_description="{what was missing or wrong in the result}".