download_image

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

Beyond the annotations (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false), it discloses the token-scoped fetch constraint (FamilySearch URLs only), the reason for disk output (multi-megabyte scans), and a copyright/redistribution caveat. No contradiction with the non-destructive, non-idempotent hints.

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?

Front-loaded with the core action in sentence one, then layered with rationale and caveats in short paragraphs. Slightly prose-heavy ('This is the step that turns a citation into evidence'), but every paragraph carries information an agent needs.

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?

There is no output schema, and the description fully covers the return behavior (file written to disk, not inlined), the auth scope, the no-overwrite rule, and the copyright caveat. Nothing an agent needs to invoke this 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 100% and the parameter descriptions are already rich, so the baseline is 3. The description adds meaning to image_url by restricting it to FamilySearch URLs (the request carries the access token), a constraint the schema does not state.

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 opening sentence states a specific verb, resource, and outcome: 'Download a document image to a local file so it can be read.' This cleanly separates it from the URL-returning siblings (get_image_links, get_film_image), which the schema explicitly says feed this tool.

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?

It gives clear context for when this is the right step ('turns a citation into evidence') and why the file is written to disk rather than returned inline. It does not explicitly name the upstream alternatives or state when not to use it, but the workflow position is easy to infer.

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