getSingleImagePostFields

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

Beyond annotations (readOnly, openWorld, idempotent), the description discloses critical behavioral details: the return is a bare array (not wrapped), the silent-fallback behavior when form_name is invalid, the exact shape of fallback responses, and that post_category values do not come from this endpoint. It also highlights a whitespace trimming issue. This adds significant value.

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?

The description is well-organized with clear sections (Use when, Required, Returns, Silent-fallback warning, post_category note). It is front-loaded with the purpose, and every sentence provides essential information without redundancy.

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?

Given the single parameter and no output schema, the description fully compensates by detailing the return format, edge cases, fallback detection, and cross-references to other tools. An agent has all information needed to select and invoke correctly.

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?

Although the schema covers the parameter with 100% description, the tool description adds examples ('blog_article_fields, events_fields') and clarifies the impact of an invalid form_name (fallback). This goes beyond the schema's 'Form slug for the post type'.

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?

The description clearly states the tool retrieves custom fields for a specific post type form, with a specific verb 'Get' and resource 'post field definitions'. It distinguishes from siblings by specifying the use case of discovering per-post-type custom fields before building create/update payloads.

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?

Explicitly states when to use ('discovering the per-post-type custom fields before building a create/update payload'), what is required ('form_name'), and provides a warning about silent-fallback with instructions to verify form_name via listPostTypes. Also gives guidance on handling post_category.

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