Retrieve a single Advanced Custom Fields value from a WordPress post by site, post ID, and field name. Choose formatted or raw output for display or processing.
Get a single ACF field value for a post
| Name | Required | Description | Default |
|---|---|---|---|
| site | Yes | Site id (see list_sites) | |
| field | Yes | Field name | |
| format | No | formatted | |
| post_id | Yes | Post ID |
Changes observed during successful MCP inspections.
v3.4.0Input schema / properties / siteAdded value: +{
+ "description": "Site id (see list_sites)",
+ "type": "string"
+}Input schema / requiredPrevious value: -[
- "post_id",
- "field"
-]New value: +[
+ "site",
+ "post_id",
+ "field"
+]v2.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It implies a read but says nothing about whether the field must exist, what happens when ACF is inactive or the field is missing, what permissions are required, or what the returned value looks like for formatted vs raw.
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 with no waste. It is arguably under-specified rather than verbose, but structurally it is clean and immediately parseable.
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 no annotations and no output schema, the description must carry the behavioral load for a 4-parameter tool, and it does not. It omits return-value shape and the formatted/raw distinction, leaving real gaps for an agent invoking it.
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 75% and the description adds nothing beyond it. Most notably it never explains the 'format' enum (formatted vs raw), which is the one parameter whose semantics materially change the result.
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+resource: retrieves one ACF field value from a post. The singular 'single ... field value' implicitly distinguishes it from the plural sibling acf_get_post_fields, though it never names that sibling 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?
No explicit when-to-use or when-not-to-use guidance. The word 'single' implies the contrast with acf_get_post_fields (bulk retrieval), but the agent must infer this rather than being routed to the alternative.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.