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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=false and openWorldHint=true, so the agent knows this is a non-destructive but non-idempotent write that reaches out to an external URL. The description adds that the image lands in the media library and that featured-image setting is an option, but does not warn about duplicate media on repeat calls (relevant given idempotentHint=false) or that featured-image changes touch a live post. Adequate, not rich.

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?

Two sentences, zero filler, front-loaded with the core action and then the optional modifiers. The final directive 'Always set alt text' is short and actionable.

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 write tool with no output schema and adequate annotations, the description covers the main flow and the two consequential options. It stops short of explaining the confirm/preview gating (left to the schema) and what happens on duplicate or failed fetches, which would have made it fully complete.

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 description coverage is only 29% (alt and confirm are documented in schema), so the description must compensate. It does: 'Pull an image from a URL' explains url, 'optionally attaching it to a post' explains attach_to, and 'setting it as the featured image' explains set_featured. Only filename and site remain unaddressed in both places.

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 specific verb and resource ('Pull an image from a URL into the site's media library') and extends scope with two named optional behaviors (attach to a post, set as featured image). No sibling tool in the list does image ingestion, so differentiation is effectively automatic; an agent knows exactly what this does.

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?

The description implies usage by naming the optional attach/featured behaviors, but never says when to use this versus a different approach (e.g., wp_write_post) or when not to. 'Always set alt text' is a directive, not routing guidance. No prerequisites or exclusions are stated.

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