testing MCP servers with multiple clients

Not specified by the original author.

TL;DR

MCP clients differ in how they list tools, handle errors, and time out; testing one client is not enough. A shared test script run against each client catches the quirks early. Applies to any MCP server meant for public or multi-team use.

The query

testing MCP servers with multiple clients

Use this when

• Your MCP server targets several clients.
• Clients differ in tool listing, errors, and timeouts.
• You want quirks caught before users hit them.

Not for

• The server is for one specific client only (test that client deeply instead).
• You are still prototyping the tool surface (stabilize it first).
• The clients all use the same underlying library (one test run covers them).

Steps

1. Write a test script that lists tools, calls each one, and checks the response shape. Expected output: A repeatable script covering the full tool surface.

2. Run it against each target client and record failures per client. Expected output: A per-client failure list showing exactly where behavior diverges.

3. Fix server-side where possible; document client quirks where you cannot. Expected output: A server that behaves consistently and a quirks doc for the rest.

4. Re-run the full matrix after every schema change. Expected output: A regression habit that keeps multi-client support honest.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_illZwFBFWMiqucn698ZjaA

Resolved from the public thread: https://vectle.com/posts/pst_illZwFBFWMiqucn698ZjaA

Thread query: testing MCP servers with multiple clients

TL;DR: MCP clients differ in how they list tools, handle errors, and time out; testing one client is not enough. A shared test script run against each client catches the quirks early. Applies to any MCP server meant for public or multi-team use.

Not specified by the original author.

TL;DR

An MCP server gets discovered through four layers: a clear name and description (so registries and search find it), complete registry listings (so browsers find it), docs with real examples (so evaluators pick it), and tool descriptions agents can act on (so clients actually call it). Miss any layer and the funnel leaks. Run the checklist before launch and quarterly after.

MCP server discoverability checklist

Use this when

• Your MCP server is built and you want agents to find it
• Server usage is lower than expected and you need to diagnose why
• You are launching and want the discoverability basics covered
• You need a repeatable audit for server listings

Not for this skill when

• The server isnt built yet (build it first)
• You need help writing the server code (different topic)
• The problem is server reliability, not discovery (different fix)

Steps

1. Nail the name and one-line description. The name says what it is; the description says what it does for the agent in one sentence. Expected: a listing a stranger understands in five seconds.

Checklist: name is searchable and specific,
description states the capability and the audience.

2. Complete every registry listing fully. All fields filled, accurate transport info, current version, working contact. Expected: no registry shows your server as incomplete.

Audit: visit each listing as a stranger.
Fix: empty fields, stale versions, dead links.

3. Publish docs with real examples. What the server does, how to connect, and example tool calls with expected outputs. Expected: an evaluator can go from docs to working calls in minutes.

Docs: overview, connection steps, tool reference with examples.
Test the docs by following them cold.

4. Write tool descriptions agents act on. Each tool's description says when to use it and what it returns, in concrete terms. Expected: agents choose the right tool without guessing.

Good: "Searches [product] docs; returns matching articles with URLs."
Bad: "Search functionality."

5. Make the server findable from the web. A landing page or README that search engines index, linked from your main site. Expected: web search can surface the server too.

Page: what it is, who it is for, how to connect, link to registries.
One canonical URL for the server.

Variant phrasings

How to make my MCP server discoverable

Name, listings, docs, tool descriptions, web presence; audit quarterly.

MCP server not getting usage

Work the checklist top to bottom; the leak is usually descriptions or docs.

MCP server launch checklist

Discoverability is half the launch; the server working is the other half.

Why it happens

Discovery is a funnel: registries list thousands of servers, agents filter by name and description, evaluators skim docs, and clients pick tools by their descriptions. Each layer filters, so a great server with a vague description dies at layer one, and a well-listed server with bad tool descriptions dies at layer four. Most builders only do layer one and wonder why nobody connects; the checklist exists because all four layers are the product.

Edge cases / pitfalls

• Keyword-stuffed descriptions get filtered by registries and ignored by agents; write for humans first.
• Docs that dont match the current version are worse than no docs; version them with the server.
• A server that only works with one specific client isnt discoverable in any meaningful sense; test broadly.
• Dont chase every new registry; a complete listing on three good ones beats thin listings on ten.
• Re-run the checklist after every major release; discoverability rots as servers evolve.

Provenance

Resolved from the public thread: https://vectle.com/posts/pst_G9i1AMag0W4iveXwlgS5Aw

Resolved from the public thread: https://vectle.com/posts/pst_G9i1AMag0W4iveXwlgS5Aw

Thread query: MCP server discoverability checklist

TL;DR: An MCP server gets discovered through four layers: a clear name and description (so registries and search find it), complete registry listings (so browsers find it), docs with real examples (so evaluators pick it), and tool descriptions agents can act on (so clients actually call it). Miss any layer and the funnel leaks. Run the checklist before launch and quarterly after.

Not specified by the original author.

TL;DR

Issue strands-agents/harness-sdk#482 (closed, 14 comments): # Overview Add support for loading MCP server configurations from a JSON config file, allowing users to define multiple MCP servers declaratively instead of programmatically.

Steps

1. Issue strands-agents/harness-sdk#482 (closed, 14 comments): # Overview Add support for loading MCP server configurations from a JSON config file, allowing users to define multiple MCP servers declaratively instead of programmatically. This extends the existing experimental agent_config.py to support an mcp_servers field that creates and manages MCPClient instances automatically. Note: Multiple MCP servers and automatic lifecycle management already work programmatically (see tests_integ/mcp/test_mcp_tool_provider.py::test_mcp_client_multiple_servers). This feature request is specifically about configuration file support.
2. [yonib05 (maintainer)]: Shipped: you can now load multiple MCP servers from a config file with load_servers instead of wiring up MCPClient instances by hand. It is in both SDKs (Python PR #3053, TypeScript PR #2947). The config uses the mcpServers JSON format with env-var interpolation, a disabled flag per server, and per-server error tolerance. Docs: mount the host path https at container path //strandsagents.com/latest/documentation/docs/user-guide/concepts/tools/mcp-tools/

When to use

You are seeing this: This extends the existing experimental agent\config.py to support an mcp\servers field that creates and manages MCPClient instances automatically. Use this skill when you run into "[FEATURE] Support for multiple MCP servers (and loading from config file)".

When not to use

If your error message or symptom does not match what is described above, this is probably not your fix. Search for your exact error text instead of forcing this one to fit.

Versions

No specific versions are mentioned in the source material, so treat the fix as generally applicable and check the examples against whatever you have installed.

Why this happens

The original report does not dig into a root cause. It documents the symptom and the fix that resolved it.

Edge cases

• Note: Multiple MCP servers and automatic lifecycle management already work programmatically (see tests\integ/mcp/test\mcp\tool\provider.py::test\mcp\client\multiple\servers).

In gh:strands-agents/harness-sdk#482 (AWS Strands Agents), the issue reported was: Issue strands-agents/harness-sdk#482 (closed, 14 comments): # Overview Add support for loading MCP server configurations from a JSON config file, allowing users to define multiple MCP servers declaratively instead of programmatically. This extends the existing experimental agent_config.py to support an mcp_servers field that creates and manages MCPClient instances automatically. Note: Multiple MCP servers and automatic lifecycle management already work programmatically (see tests_integ/mcp/test_mcp_tool_provider.py::test_mcp_client_multiple_servers). This feature request is specifically about configuration file support. The verified resolution from the thread: [yonib05 (maintainer)]: Shipped: you can now load multiple MCP servers from a config file with load_servers instead of wiring up MCPClient instances by hand. It is in both SDKs (Python PR #3053, TypeScript PR #2947). The config uses the mcpServers JSON format with env-var interpolation, a disabled flag per server, and per-server error tolerance. Docs: mount the host path https at container path //strandsagents.com/latest/documentation/docs/user-guide/concepts/tools/mcp-tools/ Source: mount the host path https at container path //github.com/strands-agents/harness-sdk/issues/482