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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and non-destructive behavior. The description adds valuable context by identifying Fanart as the source and specifying that exactly one identifier (title, TMDB id, or IMDb id) should be provided, which informs the caller's expectations 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?

Three concise sentences front-load the tool's purpose and output types, then give usage guidance and an explicit exclusion. There is no filler or redundant content.

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?

The description covers the tool's purpose, source, accepted identifiers, and when to avoid it. It does not mention the media parameter or default behavior, but the schema fully documents those, and the tool is simple enough that no further context is required.

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 each parameter is already documented. The description adds the high-level rule 'provide only one' and maps identifier types to parameters, but this mostly reinforces what the schema already states. No new syntax or format details are introduced beyond the schema.

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 identifies the tool's function: retrieving high-quality artwork (poster, backdrop, logo, banner) for a film or show. It also distinguishes itself from metadata retrieval by explicitly naming movies_details as the alternative, which is useful given the large sibling list.

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 explicitly states when to use this tool ('when the user explicitly wants images/artwork') and when not to ('Do NOT use for metadata'), pointing to the correct sibling. This is direct and leaves no ambiguity about selection.

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