odoo-mcp-relationships

name

odoo-mcp-relationships

description

Read and write relational fields in Odoo — many2one (single link), one2many (list of child records), many2many (tag-style set). Use when creating a sale.order with order lines, tagging a partner with multiple categories, adding/removing followers, replacing a set of attributes, or when writes to relational fields fail silently. Triggers on "m2o", "o2m", "m2m", "many2one", "one2many", "many2many", "relation", "tags", "followers", "order lines", "invoice lines", or any write that crosses a record boundary.

Odoo MCP — Relational field writes

Relational writes use special command tuples. Getting the command wrong is the #1 cause of silent write failures.

Many2one — single link

Just an integer ID:

# On sale.order
{"partner_id": 42}

# On crm.lead
{"user_id": 7, "team_id": 2}

To clear a many2one: {"partner_id": false}.

One2many — list of child records

The parent owns the children. Commands are tuples (op, id, vals) in a list:

Command	Meaning
[0, 0, {vals}]	Create a new child
[1, child_id, {vals}]	Update existing child
[2, child_id]	Delete child (unlink + remove from list)
[3, child_id]	Remove from list but keep the record
[4, child_id]	Add existing child to the list
[5]	Unlink all children
[6, 0, [ids]]	Replace list with these children

Create sale.order with 3 lines atomically:

execute_method(
    model="sale.order",
    method="create",
    args_json='[{"partner_id": 42, "order_line": [[0, 0, {"product_id": 101, "product_uom_qty": 2}], [0, 0, {"product_id": 102, "product_uom_qty": 5}], [0, 0, {"product_id": 103, "product_uom_qty": 1}]]}]'
)

Add a line to an existing order:

execute_method(
    model="sale.order",
    method="write",
    args_json='[[order_id], {"order_line": [[0, 0, {"product_id": 201, "product_uom_qty": 1}]]}]'
)

Update an existing line:

execute_method(
    model="sale.order",
    method="write",
    args_json='[[order_id], {"order_line": [[1, line_id, {"product_uom_qty": 10}]]}]'
)

Remove a line (delete it):

args_json='[[order_id], {"order_line": [[2, line_id]]}]'

Many2many — tag-style sets

Same commands as one2many but semantically different (no "owner"). Most common:

Add tags (command 4):

execute_method(
    model="res.partner",
    method="write",
    args_json='[[42], {"category_id": [[4, 5]]}]'  # add tag id 5
)

Remove tags (command 3 — unlinks, doesn't delete):

args_json='[[42], {"category_id": [[3, 5]]}]'

Replace all tags (command 6 — most common for "set these tags"):

args_json='[[42], {"category_id": [[6, 0, [5, 10, 17]]]}]'  # partner now has exactly these 3 tags

Reading relational fields

Many2one returns [id, display_name]:

# result["partner_id"] = [42, "Acme Inc"]

One2many and many2many return [id, id, id, ...] (just IDs):

# result["order_line"] = [101, 102, 103]
# result["category_id"] = [5, 10, 17]

To get full child records, do a second search:

order = execute_method(model="sale.order", method="read", args_json='[[42], ["order_line"]]')["result"][0]
lines = execute_method(model="sale.order.line", method="read", args_json=f'[{order["order_line"]}, ["product_id", "product_uom_qty"]]')["result"]

Dotted field access (read-only)

In domains and fields lists, you can traverse many2one and one2many:

# Orders where customer is in France
args_json='[[["partner_id.country_id.code", "=", "FR"]]]'

# Fetch related data inline
kwargs_json='{"fields": ["name", "partner_id.email", "user_id.name"]}'

Dotted paths work one level at a time: partner_id.country_id.code reads the country code of the partner of the order.

Searching many2many (gotcha)

Many2many fields require in with a list, never = with a scalar:

# WRONG — returns nothing, no error
args_json='[[["category_id", "=", 5]]]'

# CORRECT
args_json='[[["category_id", "in", [5]]]]'

This is the #1 Learned Pattern in the cookbook. If a m2m search returns empty, check the operator first.

Followers and activities

Subscribe partners as followers (via message_subscribe):

execute_method(
    model="crm.lead",
    method="message_subscribe",
    args_json='[[lead_id]]',
    kwargs_json='{"partner_ids": [42, 43]}'
)

Add an activity (reminder/todo):

execute_method(
    model="mail.activity",
    method="create",
    args_json='[{"res_model": "crm.lead", "res_id": lead_id, "activity_type_id": 1, "summary": "Call back", "date_deadline": "2026-04-25", "user_id": 7}]'
)

Debugging silent failures

1. Check the command tuple — [[0, 0, {vals}]] not [0, 0, {vals}] (commands live inside a list)
2. Check field is actually m2m/o2m — odoo://model/{model}/schema
3. For [4, id] — id must exist, or Odoo throws IntegrityError (not silent)
4. For [6, 0, [ids]] — the 0 in position 2 is the new-record placeholder, not optional