AI agents don’t choose from the whole market. They choose from an invisible approved-vendor list.

While building agent systems, I keep running into the same thing: the real competition between tools happens before anything reaches a screen.

Every agent ends up with something like an invisible approved-vendor list. It contains the tools, data sources, services, and counterparties the agent is able and permitted to consider. Nobody publishes this list, and it changes through a mixture of retrieval, registries, permissions, defaults, prior usage, and developer choices.

You can be the best tool in your category, but if you do not clear eligibility, retrieval, verification, and permission, you never get invoked. From the user’s perspective, you did not lose. You were never in the race.

A few implications keep bothering me:

• Installs are the human vote. Agent-initiated invocation is the machine vote. Most marketplaces expose the first and tell us almost nothing about the second.
• If 100 agents agree on a tool, that is not necessarily 100 independent witnesses. They may share the same base model, index, registry, evaluation data, or defaults, and therefore the same blind spot.
• Source transparency is not candidate-set transparency. You can receive a perfectly cited answer while knowing nothing about the options that were excluded before the answer was generated.

The open problem I care about is candidate-set auditability: when an agent selects three tools and silently drops thirty, can you reconstruct what was considered, what was excluded, which gate removed it, and why?

I’m curious what people building production agents are doing here. Are you logging candidate generation and elimination, or only the final invocation?

Longer version, with the broader argument:
https://ryanmerlin.com/posts/machine-attention-economy