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

Annotations already declare readOnlyHint=true and openWorldHint=true, so the read-only, external nature is covered. The description adds the billing rate ($0.008 per page), which is useful cost context not in annotations. It doesn't describe rate limits, pagination, or return structure beyond listing what's returned.

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 compact sentences that front-load the action and resource, then add return details and billing. No wasted words, though it could be slightly more front-loaded on the ID source.

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 annotations cover the safety profile and the schema covers parameters, the description adds billing and ID source context. It's largely complete for a simple read operation, though pagination behavior when requesting multiple pages isn't described.

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 100%, so both parameters are fully documented in the schema. The description adds no syntax or format details beyond what the schema provides, making the baseline 3 appropriate.

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 ('Get photos') and resource ('from a Facebook page') with the required identifier. Distinguishes from siblings like facebook_page_videos and facebook_page_posts by naming the media type and the ID source.

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?

Implies usage by specifying the page ID comes from facebook_page_details, which is useful routing. However, it doesn't state when to use this versus other page media tools or what prerequisites exist beyond the ID source.

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