Playbook

List custom fields

list_custom_fields

Read-only

List a workspace's custom fields — the structured metadata vocabulary its assets use (Priority, Season, Usage Rights), each with its field_type and the options it allows. Call this FIRST before setting or filtering a field value: it is the only source of the exact field and option spelling. A field's VALUE is set on an asset with update_asset's fields argument ({ "Priority": "High" }); there is no separate set-value tool. Field and option names are matched EXACTLY; update_asset answers an unknown one with an error naming the valid ones, and list_custom_fields has the spelling. The list also contains the workspace's built-in 'Status' field, whose value is set with update_asset_status instead. A select field holds one of its options; a date, person or url field has no options and holds one free value per asset — see update_asset's fields parameter for the value formats. Returns every field in one call — this endpoint is not paginated.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`organization`	No	Workspace slug, as returned by list_organizations. Omit it when the account has a single workspace — it is then resolved from your token. Pass it only when the account has several, or when you mean a workspace other than the obvious one.

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedOct 5, 2026

addedInput schema / additionalProperties
```
Added value: +false
```

removedInput schema / properties / context

Removed value: -{
-  "description": "Explain why you are calling this tool and how it fits into the user's overall goal. This parameter is used for analytics and user intent tracking. YOU MUST provide 15-25 words (count carefully). NEVER use first person ('I', 'we', 'you') - maintain third-person perspective. NEVER include sensitive information such as credentials, passwords, or personal data. Example (20 words): \"Searching across the organization's repositories to find all open issues related to performance complaints and latency issues for team prioritization.\"",
-  "type": "string"
-}

removedInput schema / required
```
Removed value: -[
-  "context"
-]
```

First observedOct 2, 2026

TDQS

A4.6/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover the safety profile (readOnlyHint, non-destructive, closed world), and the description layers on non-obvious behavior: exact-match semantics for field and option names, the downstream error behavior of update_asset, the presence of a built-in Status field, and the fact that the endpoint is not paginated and returns everything in one call.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Dense but front-loaded: the core purpose and the call-first instruction lead, and follow-on caveats (Status field, no separate set-value tool, matching rules, no pagination) each carry distinct information. Slightly redundant in restating that 'list_custom_fields has the spelling' after already stating exact matching, which keeps it just short of a 5.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

With no output schema, the description does the work of describing the return shape — fields carry a `field_type` and allowed options, `select` holds one option while `date`/`person`/`url` hold a free value — and it points to update_asset's `fields` parameter for value formats. Nothing an agent needs to call and then use this result is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% for the single `organization` parameter, so the schema already carries the slug format, the omit-when-single-workspace rule, and when to pass it. The description adds only implicit workspace scoping ('a workspace's custom fields') and no syntax detail beyond the schema, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('List a workspace's custom fields') and immediately defines what those are ('the structured metadata vocabulary its assets use') with concrete examples (Priority, Season, Usage Rights). An agent can distinguish it from create_custom_field and delete_custom_field without opening any schema.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives an explicit ordering instruction ('Call this FIRST before setting or filtering a field value'), names the alternative paths (update_asset's `fields` argument, update_asset_status for the built-in Status field), and states there is no separate set-value tool. When-to-use and which-sibling-to-use are both fully resolved.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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