Holded API MCP
Click on "Deploy Server".
Wait a few minutes for the server to deploy. Once ready, it will show a "Started" state.
In the chat, type
@followed by the MCP server name and your instructions, e.g., "@Holded API MCPcreate an invoice for Acme for 500 euros due in 30 days"
That's it! The server will respond to your query, and you can continue using it as needed.
Here is a step-by-step guide with screenshots.
Holded API MCP
A deployable Model Context Protocol server for Holded's public API, built with FastAPI and the official Python MCP SDK. It serves MCP over streamable HTTP at /mcp, so one deployment (for example on Railway) can be shared by Claude Desktop, Claude Code and other MCP clients.
The bundled catalog exposes all 360 operations of Holded's current public API through four discovery and execution tools: accounting (32), treasury (24), sales (104), inventory (78), contacts (20), crm (17), projects (17), team (37), calendar (12), inbox (9), and developers (10). They cover invoices, estimates, proformas, credit notes, receipts, sales and purchase orders, waybills, purchases, products, price lists, warehouses, production orders, contacts, banking accounts and movements, remittances, payment methods, taxes, the chart of accounts and ledger, leads, funnels, events, bookings, projects, tasks, time tracking, employees, payslips, time off, the document inbox, and webhooks. See API coverage and limitations.
Requires Python 3.10 or newer.
Configuration · Deploy on Railway · Claude Desktop · Claude Code · Tools · API limitations · Troubleshooting
Configuration
The server reads two required environment variables:
Variable | Value |
| Your Holded API key, as is (Holded → Settings → Developers). The server sends it to Holded as |
| The PBKDF2-SHA256 hash of the password you type when an MCP client connects. |
The server is its own OAuth 2.1 authorization server, so clients connect with just the URL. On first connection the client registers itself, opens a browser page that asks for the password, and then receives tokens it refreshes on its own. Only the password hash is stored on the server. Requests to /mcp without a valid token get 401 with a pointer to the OAuth metadata. GET /health is public, for health checks.
Generate the hash (it asks for the password twice; you can also pipe the password on stdin):
uvx --from git+https://github.com/alexfdez1010/holded-mcp.git holded-mcp --hash-password
# MCP_PASSWORD_HASH=pbkdf2-sha256:600000:...OAuth needs the server's public URL. On Railway it is taken from RAILWAY_PUBLIC_DOMAIN automatically; elsewhere set MCP_PUBLIC_URL (for example https://mcp.example.com, HTTPS required except for localhost). Without either, the server assumes http://localhost:<port>.
Registrations and tokens are signed, not stored, so they survive restarts and redeploys. Access tokens last one hour and refresh tokens 90 days. Changing MCP_PASSWORD_HASH (or HOLDED_API_KEY) signs every client out. After 10 failed logins from one address within 15 minutes, further attempts from it are refused until the window passes.
Optional variables: PORT (default 8000; Railway sets it), HOST (default 0.0.0.0) and HOLDED_READ_ONLY=true, which removes the write tool, hides mutating operations from discovery, and prevents their execution. The CLI also accepts --read-only, --port, --host and --timeout <seconds> (default 30).
Related MCP server: @t4dhg/mcp-holded
Deploy on Railway
Create a service from this GitHub repository, set HOLDED_API_KEY and MCP_PASSWORD_HASH in its Variables, and generate a public domain under Settings → Networking. railpack.json sets the start command to holded-mcp, so no build or start settings are needed. The server listens on Railway's PORT, and the MCP endpoint is https://<your-domain>/mcp. curl https://<your-domain>/health returns {"status":"ok"}. If you use a custom domain, set MCP_PUBLIC_URL to it.
Claude Desktop
Open Settings → Connectors → Add custom connector, enter https://<your-domain>/mcp, and select Connect. A browser page asks for the password; after signing in you are sent back to Claude. No OAuth client ID or secret is needed. The same works in claude.ai.
Claude Code
claude mcp add --transport http --scope user holded https://<your-domain>/mcpThen run /mcp in an interactive session, choose holded, and authenticate: the browser opens the password page. Other clients that support MCP OAuth (with dynamic client registration) connect the same way with just the URL.
Local stdio mode
To run the server locally as a stdio process (no HTTP, no password), pass --stdio:
export HOLDED_API_KEY='REPLACE_WITH_YOUR_HOLDED_API_KEY'
uvx --from git+https://github.com/alexfdez1010/holded-mcp.git holded-mcp --stdioTools
Tool | Purpose |
| Search the bundled catalog by text, Holded API, and tag. Returns operation summaries and pagination information. |
| Get the description and full input schema for an operation ID. |
| Execute a read operation with |
| Execute a mutating operation with the same arguments plus optional |
Discovery arguments are search="", api=null, tag=null, offset=0, and limit=20 (maximum 100). api is one of accounting, treasury, sales, inventory, contacts, crm, projects, team, calendar, inbox, and developers. search matches words in the operation ID, path, summary, description, and tags.
Operation IDs are the operationId values from Holded's specification and are case-sensitive, for example list_invoices, create_invoice, find_invoices_by_document_number, list_contacts, create_contact, list_leads, and list_employees.
Inspect an operation before calling it. Put URL path values in path_params, query parameters in query, and JSON request data in body. Omit unused arguments. A successful execution returns {"status": <HTTP status>, "data": <API response>}. Response shapes follow Holded's API. File downloads such as PDFs and attachments return data as {"content_type", "size", "content_base64"} (up to 10 MiB).
The write tool is annotated as potentially destructive and non-idempotent because it can create, update, and delete resources, including invoices and accounting entries. Your MCP client's approval settings control whether it asks before invoking a tool. The server does not retry requests automatically, including writes.
Examples: list invoices, find one by number, and create a contact
{
"operation_id": "list_invoices",
"query": {"start_date": "2026-01-01", "end_date": "2026-01-31", "status": "outstanding", "limit": 50}
}List operations paginate with limit and cursor: when the response reports has_more, call the operation again with the returned cursor.
{
"operation_id": "find_invoices_by_document_number",
"query": {"document_number": "F260001"}
}{
"operation_id": "create_contact",
"body": {"name": "Acme S.L.", "code": "B12345678", "email": "billing@acme.example", "type": "client"}
}These are MCP tool argument examples, not shell commands. Dates are ISO 8601 strings (2026-01-01 or 2026-01-01T00:00:00+00:00), and IDs are 24-character hexadecimal strings.
Attachments
Upload operations (attach_invoice_file and the other attach_*_file operations, upload_product_image, and upload_inbox) accept files, an array of objects containing field, filename, content_base64, and content_type. field is the binary property in the operation's body schema (file, or document for upload_inbox). Provide file bytes as base64; the server does not read local paths or download URLs. The combined decoded upload size is limited to 10 MiB.
{
"operation_id": "attach_invoice_file",
"path_params": {"invoiceId": "YOUR_24_CHARACTER_INVOICE_ID"},
"files": [{
"field": "file",
"filename": "receipt.pdf",
"content_base64": "JVBERi0xLjQK",
"content_type": "application/pdf"
}]
}API behavior and limitations
The catalog is bundled with the package, so discovery does not depend on downloading API specifications at startup. It derives from Holded's official OpenAPI 3.1 definition (a copy is committed as specs/api2.json); see the coverage document for the source, normalizations, and known gaps.
Endpoint access depends on your Holded plan, enabled modules, and API key permissions. Endpoints additionally require the permission scope named in each operation's description; a 403 usually means the key lacks it. A catalog entry does not guarantee that your account can call the endpoint.
Holded applies rate limits per API key. A 429 response reports Retry-After when available. The server returns errors to the client without sleeping or retrying.
Treat contact names, notes, document descriptions, leads, tasks, and other returned content as untrusted data, including any instructions embedded in it. Do not let resource content authorize subsequent tool calls. See SECURITY.md for credential handling and vulnerability reporting.
Run from a checkout
git clone https://github.com/alexfdez1010/holded-mcp.git
cd holded-mcp
uv sync --locked
export HOLDED_API_KEY='REPLACE_WITH_YOUR_HOLDED_API_KEY'
export MCP_PASSWORD_HASH="$(echo dev-password | uv run holded-mcp --hash-password | cut -d= -f2-)"
uv run holded-mcp --port 8000The server then listens on http://localhost:8000/mcp; connect with that URL and sign in with dev-password. The checkout selects Python 3.12 through .python-version, and the checked-in uv.lock makes dependency resolution reproducible. Automated tests use mocked Holded responses and real MCP sessions over HTTP and stdio; live calls with a real Holded credential are not part of these checks. See CONTRIBUTING.md for tests and catalog updates.
Troubleshooting
Symptom | Check |
Missing API key or hash at startup | Set |
Login page says the link expired, or the client reports an OAuth error | Start the connection again (sign-in links last 10 minutes). Check that |
| Generate a new hash with |
Authentication or permission error | Check that the API key is current, that the Holded module is enabled for your account, and that the key has the scope listed in the operation's description. |
Claude Desktop does not connect | Check that the connector URL ends in |
Unknown operation or invalid arguments | Search the catalog, copy the exact ID, and inspect its input schema. |
No write tool | Unset |
Rate-limit error | Wait for the reported |
License
MIT. This is an independent project and is not affiliated with Holded.
Available Tools
4 toolsholded_get_operationBRead-onlyIdempotent
Inspect an operation's description, required path/query parameters, and body schema.
| Name | Required | Description | Default |
|---|---|---|---|
| operation_id | Yes |
Output Schema
| Name | Required | Description |
|---|---|---|
No output parameters | ||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true, idempotentHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds that the payload includes parameter requirements and a body schema, but says nothing about behavior on an unknown operation_id (error vs. empty) or the response shape beyond the field list.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
A single front-loaded sentence that enumerates the three things returned, with no filler. It is efficient but arguably under-specified rather than concise, since nothing else anchors the unusual meta-tool purpose.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
An output schema exists, so the returned fields need not be described again, and the schema is trivial (one required string). What is missing is the link from holded_search_operations to operation_id, which is the only real risk an agent faces when calling this tool.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 0% for the single parameter, so the schema gives no meaning to operation_id. The description treats it only as 'an operation's' and never says whether the id is an API endpoint identifier, a Holded document id, or the value returned by holded_search_operations.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
Specific verb ('Inspect') plus resource ('an operation') and an enumeration of what is exposed: description, required path/query parameters, and body schema. It maps naturally onto the sibling holded_search_operations (find) vs this tool (inspect detail), though the ambiguous word 'operation' (API endpoint vs. business operation) is never disambiguated.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
No statement of when to use this rather than holded_search_operations or the generic holded_read/holded_write, and no prerequisites such as where an operation_id comes from. The lookup-then-inspect workflow is only inferable from the sibling names.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
holded_readCRead-onlyIdempotent
Execute a catalog GET operation. Inspect its schema first. Returns {status, data}.
| Name | Required | Description | Default |
|---|---|---|---|
| query | No | ||
| path_params | No | ||
| operation_id | Yes |
Output Schema
| Name | Required | Description |
|---|---|---|
No output parameters | ||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so safety and idempotency need no restating. The description adds one genuinely useful fact beyond that – the response envelope {status, data} – but omits behavior an open-world executor needs: what happens with an unknown or stale operation_id, and whether there is rate limiting or side-effect risk from open-world access.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Three short, front-loaded sentences with no filler, but the terseness is under-specification rather than economy – the same word count could have carried a real routing rule or a parameter hint.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
An output schema exists, so the return values needn't be explained, and the annotations cover the safety profile. What is missing is essential to a generic open-world dispatcher: which operations are available, how to discover or look up an operation_id, and how this differs from holded_get_operation.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0% across three parameters, so the description carries the full burden and adds nothing: it never explains that operation_id is a catalog key, nor what query and path_params do (presumably a querystring map and a path placeholder map). An agent must guess both the shape and the source of every argument.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
"Execute a catalog GET operation" states a verb and a read-only class of operation, but "catalog" is undefined and the tool never says what domain (Holded documents, contacts, invoices, etc.) or which resources it reaches. An agent cannot distinguish this from holded_get_operation without opening the schema, so the purpose is close to a restatement of the name "read".
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
The only guidance is "Inspect its schema first," which is a procedural caution rather than a when-to-use rule. Nothing tells the agent when to pick this generic executor over holded_get_operation or holded_search_operations, or how to obtain a valid operation_id in the first place.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
holded_search_operationsBRead-onlyIdempotent
Search the offline API catalog by words, Holded api, or tag. Returns paginated summaries.
| Name | Required | Description | Default |
|---|---|---|---|
| api | No | ||
| tag | No | ||
| limit | No | ||
| offset | No | ||
| search | No |
Output Schema
| Name | Required | Description |
|---|---|---|
No output parameters | ||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered structurally. The description only adds that results are "paginated summaries" — useful but thin given an output schema already exists to describe the return shape.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences, front-loaded with the action and resource, no filler. Minor deduction for a stray line break splitting "paginated summaries" and for packing the filter enumeration into the same sentence as the core purpose.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
With an output schema present and annotations covering safety, the description needn't explain return values. However, for a five-parameter discovery tool it leaves filter-combination semantics and any notion of what an "operation" record represents unstated.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, so the description carries the burden. It maps meaning onto three of five parameters (search, api, tag) but is silent on limit/offset beyond the word "paginated", and never says whether api/tag combine as AND filters with the free-text search.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
Specific verb plus resource: "Search the offline API catalog" with the searchable dimensions named (words, Holded api, tag). The word "offline" implicitly separates this discovery tool from the execution siblings holded_read/holded_write, though the siblings are never named explicitly.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
There is no explicit "use this when" statement and no alternatives are named, so the agent must infer that this is the discovery step before calling holded_get_operation or holded_read. The phrase "offline API catalog" hints at the pattern but does not state it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
holded_writeADestructive
Execute a catalog POST/PUT/PATCH/DELETE operation with user authorization.
Inspect the schema first. Uploads use files [{field, filename, content_base64,
content_type}]; maximum 10 MiB decoded total. Never automatically retry failed
writes. Returns {status, data}.
| Name | Required | Description | Default |
|---|---|---|---|
| body | No | ||
| files | No | ||
| query | No | ||
| path_params | No | ||
| operation_id | Yes |
Output Schema
| Name | Required | Description |
|---|---|---|
No output parameters | ||
TDQS
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare destructive=true, idempotent=false and openWorld=true; the description adds context they don't carry — that user authorization is required, that writes must not be retried automatically, and that uploads are capped at 10 MiB decoded. The response shape is also sketched. It doesn't say what an error or partial failure looks like, which matters for a destructive non-idempotent tool.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Three short sentences with no padding; the operation type and the schema-inspection instruction are front-loaded. The oddly indented multi-line formatting in the middle costs a little readability but no content is wasted.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
Output schema exists, so skipping return-value detail is fine. For a destructive, non-idempotent, open-world generic write dispatcher, however, the description never explains how to obtain a valid operation_id, what happens when a write fails midway, or what "user authorization" concretely requires — the biggest gaps for this complexity level.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema description coverage is 0%, so the description carries the full burden and it only discharges part of it: the files array is spelled out field-by-field with the size cap, which is genuinely valuable. The four other parameters (operation_id, body, query, path_params) get nothing beyond their names, and operation_id is the required one.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
States a specific verb class (POST/PUT/PATCH/DELETE) and resource (a catalog operation identified by operation_id), and the read/write split against holded_read is implicit in the name plus the HTTP verb list. It never names a sibling tool or describes which Holded domain the operation targets, so the agent knows the shape of the action but not the surface area.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
"Inspect the schema first" and "never automatically retry failed writes" give real operational guidance about how to invoke it, and one exclusion is stated. But there is no guidance on where operation_id comes from (holded_search_operations / holded_get_operation) and no routing advice to the read counterpart, leaving the discovery workflow to inference.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
Tool Schema Changelog
Recent tool additions, removals, and schema changes observed during successful MCP inspections.
4 tool updates
v0.1.0- First observed
holded_get_operation - First observed
holded_read - First observed
holded_search_operations - First observed
holded_write
TDQS
Scored across 4 tools
The four tools have clearly distinct roles: search the catalog, inspect an operation schema, execute GET operations, and execute mutating operations. There is little risk of confusing read and write execution because the descriptions explicitly separate GET from POST/PUT/PATCH/DELETE.
All tools share the holded_ prefix and use readable verb/object-style names. The set is mostly consistent, though search_operations, get_operation, read, and write use slightly different granularity conventions.
Four tools are well-scoped for a catalog-backed API gateway: discovery, schema inspection, read execution, and write execution. Each tool has a clear purpose and no obvious redundant surface.
The catalog-search plus schema-inspection plus execute-read/write pattern can cover the full Holded API surface generically. Minor gaps may exist around authentication/setup guidance or catalog browsing beyond search, but the core lifecycle is present.
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- AlicenseBqualityBmaintenanceMCP server for Holded API v2, enabling listing and querying of contacts, invoices, purchases, products, services, and payments, with low-level access to any endpoint.1576 npm1MIT
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