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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint, and destructiveHint=false, so the safety profile is covered. The description adds genuine behavioral context beyond that: the inline preview is model-visible and costs tokens, and can be suppressed with include_preview=false. It stops short of auth or rate-limit notes, but the preview/token tradeoff is the useful non-obvious behavior for a read tool.

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 verb and resource, and the metadata inventory is packed into a single tight sentence with no filler. Dense but every clause earns its place; only the parenthetical preview caveat is a slight interruption.

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 a full output schema, rich annotations, and 100% parameter coverage, the description only needs to frame what kind of image record is returned, which it does by listing dimensions, provenance, license, and attribution. Nothing an agent needs to invoke it correctly is missing from the combined definition.

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% across all 6 parameters, so the schema already documents id formats, locale enum semantics, context, llm_model, and conversation_id handling. The description only echoes include_preview's effect ('unless include_preview is false'), adding nothing beyond what the schema states. Baseline 3 is correct.

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 ('Fetch') and resource ('one image') and enumerates the metadata returned, which clearly separates it from lookalikes such as search_images or download_image. It does not name a sibling explicitly, but the singular 'one image by id' scope is unambiguous.

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 id-based fetch and the metadata list, but the description never states when to prefer this over download_image (get the file) or search_images (find by query), nor any prerequisite such as needing an id from search results. No explicit alternatives or exclusions.

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