Agents can call APIs, but granting them access is a permission decision—not just a matter of adding an MCP server. In an engineering account, Nikolas Dimitroulakis argues for reusing the requests and tests a team already trusts, exposing only selected operations, and making access changes visible in code review. His examples show why a developer’s own coding agent, an outside agent, and an MCP server under test need different boundaries.
Why API access for agents needs a deliberate boundary
“Who called your API last?” is the question behind Nikolas Dimitroulakis’s argument in “Your API’s newest users are agents…”. He describes encountering agents more often as API callers, but this is a qualitative observation, not a measured industry trend. The practical concern is clearer: existing API workflows often assume a developer manually constructs and sends each request, while an agent may need to discover and execute operations on its own.
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There are three different situations to plan for: a team’s own coding agent working with project requests, an outside agent allowed to perform a narrowly defined action, and testing an MCP server before relying on it. Treating them as one access problem obscures who is trusted, which operations are available, and what happens when a test fails.
When a coding agent needs to debug a request
Dimitroulakis’s first example is a checkout request that returns HTTP 400. Without access to the request itself, a developer might paste the error or a curl command into a chat. The agent may then guess at headers or ask where the token belongs. If the request already lives in the project repository, the agent can instead inspect and run that known request, then examine the real response to find a missing header.
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In the author’s account, Voiden lets the agent list, run, and inspect the project’s existing requests. He says this setup is enabled for the whole project by default because the trust boundary is the developer, their editor, and their own agent. That is a local-team choice, not a safe default for every repository: a project containing production credentials may call for a narrower boundary.
When an outside agent should perform only one action
Consider a support assistant that needs to issue refunds, but should not be able to perform other account or payment operations. A separate MCP server can entail another schema, authentication wiring, secret management, integration, and hosting. If its description of the API is maintained independently from the requests the team tests, the two can drift apart.
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The alternative Dimitroulakis describes is to reuse a written and tested request, explicitly mark it as an agent tool, and choose which inputs the agent may provide. In his refund example, the agent supplies only an order ID; credentials remain in the environment rather than being exposed as agent-controlled values. The author’s line is: “Nothing is exposed until you mark it.” This reduces duplicated descriptions, but it does not replace authentication, authorization, or careful handling of secrets.
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Make test status part of the access policy only by choice
Dimitroulakis’s approach makes a tool available only while its tests pass. A failure removes the tool from availability. He favors that strict policy because he would rather temporarily lose access than let an agent use an operation that has not been verified recently, while acknowledging that flaky tests can make the experience frustrating.
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This is a policy choice, not a general MCP requirement. Teams considering it should decide how the agent and its user will learn that a tool is unavailable and whether a transient or flaky test should block an operation. The account does not specify an explanatory error behavior.
Testing an MCP server before depending on it
Testing has two distinct uses in the article: checking a team’s own MCP server before release, and inspecting a vendor’s server before building on it. An ephemeral inspector session or one-off script can help with a quick check; saving a call with assertions makes it repeatable in CI.
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The author gives examples such as asserting that search_orders returns the expected shape and keeping a working reference for Notion’s server. These are examples from his account, not independent claims about Notion’s current capabilities. The useful distinction is between an interactive inspection and a saved test that can be rerun as the server or its dependencies change.
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Keep requests, tests, and permissions reviewable together
The central design principle is one maintained description of an API operation rather than separate versions for manual testing, agent execution, and tool publication. Dimitroulakis puts it this way: “One description of the API, instead of three that slowly disagree.” When that description is in the repository, a change to which values an agent controls—or which operation it can call—can appear in a pull request.
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A review trail helps maintainers see a permission change; it is not proof that the change is secure. Reviewers still need to evaluate the operation’s scope, agent-controlled inputs, credential handling, and test behavior. As the author says, “Permission decisions deserve a review trail.”
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How the three cases differ
| Use case | Trust boundary | Access scope | Design concern |
|---|---|---|---|
| Team coding agent | Developer, editor, and the team’s own agent | May use project requests; the author enables this across a project by default | Decide whether the repository’s credentials and endpoints belong inside that boundary. |
| Outside support agent | An external agent that should have limited authority | Explicitly selected operation and limited agent-supplied inputs, such as an order ID | Keep secrets out of agent-controlled inputs and review access changes. |
| MCP server validation | The team’s own server or a vendor’s server being evaluated | Saved calls and assertions for the operations being tested | Use repeatable checks when a one-off inspection is not enough; decide whether test failure should disable a tool. |
Check protocol requirements separately from the workflow
MCP is evolving. The project’s announcement for the 2026-07-28 specification describes a stateless protocol core and authorization changes, including validating the iss parameter in authorization responses and binding credentials to the issuer that minted them. It also describes changes to discovery and caching. These are protocol-level developments; Dimitroulakis’s workflow should not be assumed to implement that revision. Before building or deploying an MCP integration, consult the dated specification announcement and the current normative specification for the requirements that apply to your implementation.
The MCP project’s server overview is identified as draft material and describes tools as executable functions that can let models take actions or retrieve information, including through API requests. Treat draft guidance as context, not as a stable requirement.
A separate developer tutorial on agent-friendly APIs discusses discoverability, structured responses, safety, and idempotency. Its examples include an /actions endpoint and an idempotency-key mechanism, but it warns that its in-memory store and simplified schema validation are not production implementations. Those examples can inform design discussions; they do not establish that every agent-facing API needs that endpoint pattern.
Quick Recap
A practical review checklist
- Identify the caller: Is this the team’s own coding agent, an outside agent, or a server being tested?
- Limit the scope: Decide which operations are available and which values the agent may set.
- Choose the source of truth: Prefer requests and tests the team already maintains over a second, independently handwritten description where practical.
- Set failure behavior: Decide whether a failed test blocks access, how flaky tests are handled, and how unavailability is explained.
- Review credentials and changes: Keep secrets in the appropriate environment and make permission changes visible to maintainers; neither practice replaces access controls.
- Verify protocol version: Check current MCP authorization and other normative requirements rather than inferring them from an older workflow or draft page.
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