Newegg PC Builder MCP Skill

Connects Claude to the Newegg PC Builder MCP service. This skill is

fully dynamic: it discovers available tools at runtime and lets the LLM

decide which tool to call and how to fill its parameters. No tool names or

parameter names are hard-coded, so the skill continues to work even after

the MCP server updates its API.

MCP Endpoint: https://apis.newegg.com/ex-mcp/endpoint/pcbuilder

Script: scripts/mcp_client.py

Core Workflow (always follow this order)

Step 1 — Discover tools

Always start by listing available tools. Never assume tool names or parameters

from previous runs or documentation.

python scripts/mcp_client.py list_tools

The output contains, for each tool:

• name — identifier to use when calling
• description — what it does (may be empty; infer from name + schema)
• inputSchema.properties — available parameters with types and descriptions
• inputSchema.required — mandatory parameters

Step 2 — Select tool and map parameters

Read the list_tools output and decide:

1. Which tool best matches the user's intent?
• Match on description first; fall back to inferring from name + param names
• If multiple tools apply, prefer the most specific one
• If still ambiguous, pick the first one and note the assumption

1. How does user intent map to parameters?
• Only use parameters present in inputSchema.properties
• Free-text params (e.g. question, query, text): pass the user's

request as a natural-language string describing their need

• Typed/enum params: map user intent to the closest valid value
• Leave optional params unset unless you have a clear value
• Never invent parameters not present in the schema

Step 3 — Call the tool

python scripts/mcp_client.py call <tool_name> '<json_arguments>'

Tool name and arguments are determined at runtime from Step 2. Example:

python scripts/mcp_client.py call v2allin '{"question": "gaming PC RTX 5090 9800X3D best price"}'

Windows PowerShell (important)

PowerShell parses outer double quotes before Python runs. Using \"...\" inside "..." often breaks the JSON string (you may see errors like Got: {\ or “invalid JSON”). Prefer one of:

1. Single-quote the whole JSON (no backslash escapes needed):

```powershell

python scripts/mcp_client.py call v2allin '{"question": "gaming PC RTX 3070"}'

```

1. JSON in a file (most reliable for long or nested payloads):

```powershell

Set-Content -Path args.json -Encoding utf8 '{"question": "gaming PC RTX 3070"}'

python scripts/mcp_client.py call v2allin @args.json

```

1. Stdin (pipe or redirect):

```powershell

'{"question": "gaming PC RTX 3070"}' | python scripts/mcp_client.py call v2allin -

```

The script supports @path\to\file.json and - for stdin so shells never need to escape inner double quotes.

Where to change things

• Skill + script (recommended): keep examples and mcp_client.py in sync — document PowerShell rules here, and use @file / - in the client to avoid quoting bugs.
• Repo-only docs do not fix agents that load this skill from ~/.agents; updating the skill is the right place for portable behavior.

Step 4 — Interpret the response

Parse the JSON output. Common response shapes:

{ "result": { "summary": "...", "popular": [...], "valued": [...] } }

• summary non-null → use as the primary answer text
• popular / valued arrays present → list the builds
• All result fields null → service returned no data; tell the user and offer

to answer from general knowledge instead

• isError: true → report the error and suggest retry

Step 5 — Present results

• Build list: name, total price, key components, brief description
• Compatibility check: clear yes/no with reasoning
• Component details: specs, price, compatibility notes
• No results from API: explain clearly, then offer a manual recommendation

Edge case handling

| Situation | Action |

|-----------|--------|

| list_tools returns 0 tools | Report service unavailable; answer from training knowledge |

| Tool description is empty | Infer purpose from name + parameter names |

| Schema has no required | Treat all params as optional; pass what you have |

| All response fields null | No data for this query; say so and fall back to general knowledge |

| HTTP error on list_tools | Report error; do not proceed to call step |

| HTTP error on call | Retry once; if still failing, fall back to general knowledge |

| Multiple tools match | Pick most specific; briefly note the choice |

Script reference

scripts/mcp_client.py uses Python standard library only (3.6+, no pip needed).

Handles both application/json and text/event-stream responses automatically.

python scripts/mcp_client.py list_tools
    → prints all tools with full parameter schemas

python scripts/mcp_client.py call <tool_name> '<json_args>'
    → calls the tool and prints the JSON response

python scripts/mcp_client.py call <tool_name> @args.json
    → reads JSON arguments from a UTF-8 file (good on Windows)

echo '<json>' | python scripts/mcp_client.py call <tool_name> -
    → reads JSON from stdin

Errors go to stderr with a non-zero exit code. Invalid JSON prints a short hint for PowerShell users.