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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, openWorld), and the description adds substantial non-obvious context: a $0.005 USDC cost per successful call via x402/Solana, a ~190KB input cap tied to the 256KB POST-body limit, and the fact that pixels are not decoded. These cost and size constraints materially affect invocation decisions and are not derivable from annotations or schema.

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 front-loaded with the core capability and output fields before cost and transport details. It is dense and mostly earns its space, though the body/size-limit detail partially duplicates the schema and could be trimmed.

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 output schema, the description compensates by enumerating the returned fields (format, dimensions, megapixels, animation, sha256, EXIF summary) and disclosing pricing, input limits, and an alternate HTTPS endpoint. An agent has enough to decide whether to call it and how to supply input 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?

Schema description coverage is 100%, so both parameters (image and include_exif_tags) are fully documented in the schema. The description repeats the base64 body shape and size cap but adds no new meaning for include_exif_tags or the accepted formats beyond what the schema states; baseline 3 is 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 ('Inspect') and resource ('an image') and immediately enumerates the exact outputs returned (format, dimensions, megapixels, animation, sha256, EXIF summary), so the agent knows precisely what the tool produces. The 'without decoding pixels' qualifier further distinguishes it from image-manipulation siblings like image_resize or format_convert.

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?

Usage is implied by the purpose ('inspect an image' when you need metadata), but there is no explicit when-to-use/when-not guidance and no named alternative among siblings such as image_resize or format_convert. The HTTPS endpoint mention is a transport alternative, not a tool-selection guideline.

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