> ## Documentation Index > Fetch the complete documentation index at: https://iotools.cloud/docs/llms.txt > Use this file to discover all available pages before exploring further. # Tools over MCP > What's exposed, how names map, and what it costs ## What's exposed **800+ tools on the site.** If a tool page's **Builder** menu shows "MCP", an agent can call it. The rest run entirely in the browser — webcam capture, some PDF and image editing — and have no server-side equivalent. Calling one returns `tool_not_allowed`, so an agent knows to stop retrying and send the user to the website. ## Name mapping MCP tool names can't contain `/`, so nested slugs use a double underscore: ``` html-generator/button → html-generator__button converters/color/hex-to-rgb → converters__color__hex-to-rgb ``` Flat slugs are unchanged. ## Finding and running a tool A hosted session lists five tools, not all — see [the overview](/docs/mcp/overview) for why. Three calls get from "convert a CSV" to a result: ```json theme={"system"} { "query": "csv to json", "limit": 3 } ``` Returns: ```json theme={"system"} { "tools": [ { "name": "csv-to-json-converter", "title": "CSV to JSON Converter", "description": "Convert CSV data to JSON…", "credit_cost": 3 } ] } ``` ```json theme={"system"} { "name": "csv-to-json-converter" } ``` Returns: ```json theme={"system"} { "name": "csv-to-json-converter", "slug": "csv-to-json-converter", "title": "CSV to JSON Converter", "credit_cost": 3, "credit_cost_multiplier_field": null, "input_schema": { "type": "object", "required": ["ioCsvInput"], "properties": { "ioCsvInput": { "type": "string" } } }, "output_schema": { "...": "..." }, "docs_url": "https://iotools.cloud/tool/csv-to-json-converter/" } ``` ```json theme={"system"} { "name": "csv-to-json-converter", "inputs": { "ioCsvInput": "a,b\n1,2" } } ``` Charged 3 credits — exactly what `describe_tool` quoted. Search and describe are free. Always describe before you run: field names aren't guessable. `credit_cost_multiplier_field` names the input that multiplies the price on per-unit tools (`ioCount` on the name generators, at 2 credits a name). `null` for the flat-priced majority. Connect to `?listing=full` to get all supported tools with their own schemas instead — worth it only if your client loads tools lazily. Either way a tool can be called by its own name directly. Over REST the equivalents are [`GET /v1/tools/search`](/docs/api-reference) and `GET /v1/tools/list`. ## Inputs Inputs use the same names as the REST API (`ioInputString`, `ioCase`, …), advertised through `describe_tool`'s `input_schema` — or, under `?listing=full`, through each tool's own `inputSchema`. They are the same object either way. ## Results A successful call returns both text content and `structuredContent` — the same `outputs` object REST returns, so an agent can read fields by name. Failures come back as an MCP error result carrying the [same error codes](/docs/concepts/errors) as REST, as `code: text`: | `code` | Example text | | ---------------------- | ----------------------------------------------------------------------------- | | `validation_error` | `{"ioBase64String":"Required"}` | | `tool_not_allowed` | `"Background Remover" is available on iotools.cloud but has no API endpoint.` | | `insufficient_credits` | `0 remaining` | Parse the prefix up to the first colon — the text after it varies by code (a field map, a sentence, a short phrase) and isn't guaranteed stable. ## Checking your balance Alongside the three above, hosted MCP sessions get two tools that aren't from the catalog. `get_credits` takes no arguments: ```json theme={"system"} { "tier": "member", "metered": true, "credits": { "used": 412, "limit": 1000, "remaining": 588, "period": "month", "resets_at": "2026-08-01T00:00:00.000Z" }, "rate_limit": { "requests_per_minute": 60 } } ``` It **costs no credits**, so an agent can check whether it can afford an expensive tool without paying for the answer. It still takes your per-minute rate limit — use it before a batch, not on a loop. It is not offered over the local stdio server, which runs on your own machine with no API key and no metering, and so has no balance to report. ## Reading your usage history And the fifth, `get_usage` — also no arguments: ```json theme={"system"} { "days": 30, "credits": { "used": 412, "limit": 1000, "remaining": 588, "period": "month", "resets_at": "2026-08-01T00:00:00.000Z" }, "items": [ { "day": "2026-07-28", "slug": "ai-writer", "title": "AI Writer", "surface": "api", "credits": 24, "runs": 1 }, { "day": "2026-07-27", "slug": "case-converter", "title": "String Case Converter", "surface": "mcp", "credits": 3, "runs": 1 } ] } ``` What the balance doesn't tell you is what it went on. No credits, last 30 days of spend — one row per tool per day per surface (`web`, `api`, `mcp`), so browser and REST use show up here too. Same stdio carve-out as `get_credits`. `credits` is the same object `get_credits` returns, from the same builder, so the two can't quote different numbers — it's here because spend and balance answer each other's obvious follow-up. It's `null` only on an unmetered deployment. Use `get_credits` when the balance is all you want: it also carries your rate limit and per-plan credit floor. Over REST, [`GET /v1/me/usage`](/docs/api-reference) returns the history alone — pair it with `GET /v1/me/credits` for the balance. ## Cost Every tool call is metered and refunded on failure — see [Credits](/docs/concepts/credits) for the per-plan floor. `run_tool` costs the same as calling the tool directly: no surcharge, no discount. Listing is free, and so are `search_tools`, `describe_tool`, `get_credits` and `get_usage`.