Troubleshooting the Chemia materials MCP connector

Why does opening the connector URL in a browser show an error?

The connector URL is an endpoint for MCP clients, not a web page, so a browser has nothing to show and no sign-in to offer.

What we observed on 2026-10-04:

• A request to the connector URL without a sign-in returns HTTP 401, with a WWW-Authenticate header that points to the protected-resource metadata.
• The bare host name, without the /mcp path, returns HTTP 404.

Use the full address, https://mcp.chemiadiscovery.com/mcp, in an MCP client. The Connection guide shows how.

What if sign-in fails or my account is not found?

Sign-in needs an Elixir account that an administrator has approved. To ask for one, use the Elixir sign-in page and its sign-up option.

An account that holds no grants still connects, but it sees only the tools that need none: list_capabilities and list_material_sources. See Access, grants and limits.

Why can I not see a tool that I read about here?

The server's access rule is: "A caller needs any one of the grants listed for a tool. A tool with no grants listed is open to every authenticated caller. A tool the caller was not granted is hidden from tools/list and refused if called."

A tool that your account may not call is therefore missing from the list rather than shown and disabled. The grants table in Access, grants and limits says which grant each tool needs.

A new grant does not show up. What should I do?

Your grants travel with your sign-in token. A change to your grants reaches an open connection when the token is next refreshed. To see it sooner, disconnect the connector and connect again, which signs you in afresh.

I reached the daily limit. What now?

The charged tools (compute_pourbaix_stability, count_materials and search_materials) stop when your daily allowance of 200 charged calls per day is spent (a declared default that a deployment can override, as of 2026-10-04). The window is one calendar day, counted on the server host's local date (the counter keys on the host's date.today()); the refusal message gives a reset time of midnight labelled UTC after that date, so the two agree only where the host runs in UTC.

Tools that are not charged keep working when the allowance is spent. The limit resets at the end of the window.

Details are in Access, grants and limits.

Why did a tool answer from the trial subset instead of the dataset I asked for?

Check source in every response. A source_id that is misspelt or not in the catalogue raises no error: it resolves to the registry default, the small trial subset, and requested_source then names that default too, so only a comparison with the id you sent shows the swap. A restricted dataset that was inferred from the query text, or taken as the server default, is narrowed to the trial subset without an error when your account lacks the professional_database grant; there requested_source differs from source.

This note is from the search_materials reference. The other dataset-scoped tools follow the same rule.

Why does get_material_property say not_found for a property that exists?

A property name that is not the stored key is not an error. It reads as status not_found, "no measured value", which looks like missing data. Use the canonical key; property_stats and plot_distribution return did_you_mean for names they do not know.

This note is from the get_material_property reference.

Why did the tool ask me a question instead of returning results?

When a request is too vague to run, or matches more materials than a search can store, the tool returns clarification_needed instead of guessing. For a request that is too large it adds a size estimate and ways to narrow it. A reply that asks a clarifying question is refunded, so it does not use your daily allowance. The search_materials reference has the details.

How do I report a problem?

Use Contact support. Please include the tool name, the arguments you used, the error text and roughly when it happened.