Test MCP Tools with the Embedded MCP Inspector

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Availability

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Overview

The embedded MCP Inspector lets you test an MCP product’s tools directly from the Live Portal, so you can validate a connection and see what a tool returns before writing any agent code.

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Open the Inspector

The Inspector is available for MCP-typed products only, and appears in two places. On the Product’s detail page, the Service explorer tab embeds it inline under a Try it toggle (Instructions shows the operator-authored markdown instead). Selecting Try it out on an individual service opens that service’s own documentation page, which shows the same Try it / Instructions toggle. Once the Inspector loads:

1. It lists the tools the MCP server exposes.
2. Select a tool to see its input parameters.
3. Fill in the parameters and call the tool. The response appears in the same view.

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How the Inspector Connects

The Inspector does not connect to your MCP server directly. The Portal sits in between and connects to the MCP server URL configured on the product. You cannot point the Inspector at a different server. The Portal only allows a connection to the server of the product whose page you opened.

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Saved Settings and the Seeded Server

In v1.20.0, the Inspector opens with the product’s MCP server already added and named after the API. If the Portal cannot find the server URL, the list is empty and you can add a server yourself. The Portal saves each developer’s server list and OAuth credentials, so they survive a Portal restart. They belong to one developer, on one product and API, for one login session. Signing in again starts fresh.

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Providing Credentials

Unlike the GraphQL Playground, the Inspector does not automatically populate your credentials. Enter your issued credential into the Inspector’s connection form yourself. The Portal’s proxy forwards it to the MCP server without reading or modifying it. See Access protected MCP proxies with OAuth 2.1 for how the Portal surfaces credentials and token information for a PRM-protected MCP proxy.

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Configuring the /fetch Endpoint’s SSRF Guard

The Inspector uses a generic HTTP fetcher, /fetch, for OAuth and PRM metadata discovery (for example, resolving an authorization server’s metadata document). This is separate from the MCP JSON-RPC proxying described above and does not affect tool calls. Both Inspector versions use these settings. PORTAL_MCP_INSPECTOR_BLOCKPRIVATEFETCH defaults to true for security (to prevent SSRF). For local development against a Gateway or authorization server on localhost or a private network address, it needs to be set to false. The Portal logs a startup warning while it is off. Turning it on only affects /fetch (OAuth/PRM metadata discovery), not the Inspector’s ability to call MCP tools. If your authorization server or its metadata endpoint is only reachable at a private or internal address, enabling this setting blocks the Inspector from reaching it.

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Inspector Versions

The Portal includes two versions of the MCP Inspector and shows one of them on MCP product pages.

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Choosing the Inspector Version

Both versions are always available. The PORTAL_MCP_INSPECTOR_USEV2 setting only decides which one the product page shows. It is false by default, so the page shows V1 until an operator turns it on. Setting it back to false returns the page to V1.

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Protocol Negotiation

MCP inspector V2 connects with the handshake set in PORTAL_MCP_INSPECTOR_PROTOCOLERA. The default, auto, tries 2026-07-28 first and falls back to the 2025-11-25 handshake if the server does not support it. Developers cannot change this in the Inspector. The following settings control the Inspector versions.

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Troubleshooting