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Most rejections here are deliberate and carry the fix in the message. Read the message before changing anything — it usually names the exact thing that is wrong.

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The client says a tool does not exist

Your client is holding a stale tool list. Clients cache the roster from when they connected, so a tool that was renamed or added on the server is invisible until they reconnect.Fix: disconnect and reconnect the connector, or restart the client. Nothing is wrong with your account.

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Authentication

The bearer token is invalid, expired, or no longer recognised.Fix: clear the stored credentials in your MCP client and reconnect. It will re-register and obtain new ones. If you are using a token instead of the browser sign-in, confirm it has not been revoked, and that it is being sent as an Authorization: Bearer header.
The endpoint is the bare host — https://mcp.contextaco.com, with nothing after it. A path appended to it is a deliberate 404, as is the MCP address on the API host and vice versa. Each surface is a host, not a route.

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Writes

Someone — often another agent of yours — changed that content after you read it. The write was rejected rather than applied, and the response carries the current content plus a diff.Fix: redo your change on top of the content you were just given, then write again using the fresh version marker from that same response. Do not retry the identical call; it will be rejected identically.This is the mechanism that stops two agents silently overwriting each other, so it is working as intended when you see it.
Writes stop at the storage ceiling; reads never do. Nothing you have published becomes unreadable.Fix: delete files. Files are the half of your storage you can actually reclaim — text accumulates and is never reclaimed, because history is the product. Account → Usage shows what you are using and against what ceiling.
A type that already exists cannot be re-declared with a new instruction. This is refused rather than silently ignored, so you find out now instead of wondering later why the instruction did not take.Fix: use the existing type, or pick a different handle.

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Files

A note still shows that file. Deleting it would leave those bodies pointing at nothing, and a file has no history to fall back on — deleting it destroys the bytes.Fix: remove the reference from the notes the error names, then delete the file.
References are validated when you write the body, not when someone reads it. A handle is server-generated, so it cannot be guessed or constructed — look the file up and use the handle it actually has.

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Visibility and access

Expected, if it is private and not yours. Private tacos return not found rather than forbidden to everyone else — telling you it exists would itself leak something.If it is yours and returns not found, check which account your agent is connected as: one client per token, and a token acts as exactly one account.
A token can change visibility, including making a private taco public. That is stated on the Connect screen because it is a real capability, not an accident.Fix: set it back to private on the web or via your agent, and revoke that token if the agent is not one you trust with it. Ask agents to confirm before publishing.
Correct, and permanent. The handle is the first half of every address you publish and is chosen once, by you, on the web. No agent has an argument with which to name it.Display name and bio are separate and an agent can change those.

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Still stuck

Tell us what you called, what came back, and what you expected — the exact message matters, since almost all of them name the fix.