AI agent tool fallback after the installed tool set fails
Separate an agent's failure to find a suitable installed tool from provider execution, then resolve only the missing capability.
Read the guideTechnical guides
How production agents find the next tool.
These guides separate protocol discovery, public registry metadata, runtime capability selection, provider execution, and outcome evidence. Each page is written for builders and cites the primary contracts on which it relies.
Seven distinct problems
Start with the layer that is failing
MCP can list tools on a connected server. Production agents still need an answer for missing servers, client-specific connection paths, competing candidates, definition drift, and measured reliability.
MCP tool discovery within and across servers
Understand what MCP discovers natively, what a registry contributes, and what an agent still needs before choosing among providers.
Read the guideDynamic tool discovery without loading every schema
Load the smallest eligible tool set for the current task, while treating new or changed definitions as untrusted runtime input.
Read the guideMCP registry versus capability router
A registry answers what has been published; a capability router answers which currently eligible connection best fits this bounded intent.
Read the guideChatGPT MCP compatibility across web and desktop
Choose the ChatGPT surface first: hosted plugin tools on the web and local Codex-host configuration on desktop are different compatibility questions.
Read the guideMCP server compatibility in Codex
Codex supports stdio and Streamable HTTP, but provider documentation, authentication, permissions, and product restrictions still decide the real result.
Read the guidePrepare for the MCP 2026-07-28 release candidate
Inventory session and initialization dependencies, review deprecated features, and treat client support as unknown until its owner publishes evidence.
Read the guideEditorial boundary
Useful before promotional
The guide library will grow only when search queries, public demand aggregates, or builder questions justify a distinct page. Similar keyword variants remain one page.
Primary contracts
Protocol mechanics link to the official MCP documentation; platform-specific behavior links to the platform owner.
Measured product claims
ResolveMesh performance and eligibility claims point to the published methodology or current product contract.
Sparse-by-design evidence
No provider becomes eligible because it appears in a registry, a guide, or a paid relationship.