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

Annotations declare non-destructiveHint, but the description adds the crucial nuance that set_featured REPLACES the visible featured image (a live-site change requiring confirmation and returning a preview), while the original remains recoverable. This goes well beyond the annotations.

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?

Front-loads the primary action and consequences, then handles the featured-image branch; dense but each clause carries information. Slightly long but justified by the branching behavior.

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?

For a 7-parameter mutation tool with no output schema, it covers the risky paths (overwrite semantics, featured replacement, confirmation flow, alt-text requirement). Missing coverage of filename/attach_to semantics keeps it from a 5.

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 only 29%, but the description supplies the semantics of the two most consequential parameters: set_featured (makes the image the post's featured image) and confirm (needed only with set_featured, otherwise previews). It does not cover filename or attach_to, leaving a modest gap.

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 precise verb+resource ('Add an image from a URL to the site's media library') and disambiguates from sibling write tools like wp_write_post and wp_replace_in_post by describing the media-library placement and optional featured-image side effect.

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?

Explicit conditions: use confirm: true only when set_featured is true and after user agreement; the no-overwrite case is stated as the default path. The 'Always set alt text' rule functions as a usage requirement.

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