get_film_image

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

Annotations cover read-only/open-world safety, but the description adds real behavioral context beyond them: it validates via the thumbnail first so a bad film/image number yields a clear error rather than a broken URL, and it discloses that the thumbnail requires no token while the full page does. That auth distinction is valuable for a tool whose result depends on credentials.

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 purpose, then the citation rationale and the thumbnail/token behavior. Every sentence carries information, though the opening ark-contrast and the source-pointer sentences could be tightened; nothing is filler.

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 still explains the validation path and the token requirement for the full image, which is the key operational nuance. Combined with 100% schema coverage on both required params and read-only annotations, an agent has what it needs; only the return shape of the thumbnail-vs-page result is left implicit.

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 already documents both parameters including the leading-zero requirement and 1-based image numbering. The description reinforces the citation-sourced semantics of the two fields but adds no format or syntax detail beyond the schema, so the baseline 3 applies.

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 and resource ('reach a page image by film and image number instead of by ark') and immediately contrasts the addressing mode with the ark-based alternative. The sibling references (get_record_image, get_catalog_entry) let an agent distinguish it from other image tools without opening the schema.

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?

Clearly says when to use it: when a citation names a film (DGS) and image rather than an ark, and names where those numbers come from (get_record_image, get_catalog_entry). It does not mention when NOT to use it or point to sibling alternatives such as get_image_links/download_image, so it stops short of a full when/when-not statement.

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