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

Annotations already declare this a safe, idempotent, non-destructive local read, so the bar is lower; the description still adds real value by enumerating what comes back (metadata, credit line, licence, page link) and disclosing the paid-scene branch that returns a purchase link instead. The explicit 'Does not return SVG source' caveat prevents a common misuse. Error behavior for a missing id is the main omission.

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 short sentences, front-loaded with the action and id format, then return content, then the negative constraint. Every sentence adds information an agent would otherwise have to guess.

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 single-parameter read tool with no output schema, the description covers identification, return contents, paid-scene variation, and the key exclusion. Combined with the rich annotations, nothing needed to call it correctly is missing.

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 0%, so the description must carry the parameter meaning — and it does, supplying the concrete 'fanio:<pack>/<scene>' format that the bare string schema with only maxLength=140 lacks. It does not explain how to obtain such an id, which keeps it from a 5.

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 uses a specific verb and resource ('Get one scene by id') and pins down the id shape as 'fanio:<pack>/<scene>', which lets an agent distinguish it from collection-oriented siblings like search_scenes. It stops short of naming a sibling explicitly, so differentiation is implied rather than stated.

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 only implied by 'by id' — the description never states when to prefer this over search_scenes or get_pack, nor any prerequisite such as where the id comes from. There is no when-not guidance at all.

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