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

Annotations already declare readOnly/idempotent/non-destructive, so the safety profile is covered. The description adds real value beyond them: it asserts no images are created and characterizes the return as pictures of three distinct kinds, which the annotations cannot express.

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-loads the core purpose and the negation ('creates none') before parameter details and the use case. Slightly wordy and line-wrapped, and the use-case sentence would read better ahead of the parameter enumeration, but no sentence is wasted.

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 rightly characterizes the return (portrait, reference sheet, gallery). It is nearly complete for a three-parameter read tool; ordering when `which=all` and the interaction between `which` and `limit` are 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 0%, so the description must carry the parameter burden, and it does: it enumerates the legal values of `which` (portrait, reference_sheet, gallery, all) that the schema leaves as an unconstrained string, and states the `limit` range of 1-6. Only `character_id` is left unstated, which is self-evident from the name.

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?

Names a specific verb and resource ('images already saved for a character in LoreKeeper') and enumerates the returned artifacts: portrait, reference sheet, gallery. It also explicitly distinguishes itself from the picture-making sibling by saying it 'returns existing images and creates none'.

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?

Gives a concrete use case ('For a visual reference when describing or recreating the character') and a negative boundary that implicitly routes the agent to make_character_picture when it needs new images. It does not name that sibling explicitly, so the routing is clear but inferential.

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