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

With no annotations provided, the description carries the full burden and does meaningful work: it discloses URL expiry ('about an hour'), states 'Read only: never regenerates anything,' and implies the operation is a pure retrieval. It does not say what happens when a character has no reference sheet yet or whether URLs require authentication, which are the remaining gaps.

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?

Four short sentences, each carrying distinct information: what is returned, how to use it, expiry, and the read-only guarantee. The most actionable detail (the referenceImageUrl hand-off) is front-loaded immediately after the purpose.

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 must convey return values, and it does — two URL sets plus their one-hour lifetime. Only the failure mode (character existing but with no generated sheet) is unaddressed, for an otherwise simple single-parameter read tool.

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?

There is a single required parameter with 100% schema description coverage, so the schema already establishes characterId as a UUID. The description adds the useful semantic link that the character is the subject whose reference images are returned, giving a baseline-plus score.

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 opens with a specific verb and resource — 'Get fresh URLs of a character's reference material: its base image and the 16-shot reference sheet' — and enumerates exactly what is returned. It is clearly distinct from the sibling ryla_generate_character_sheet, which creates the sheet rather than retrieving URLs for it.

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 concrete downstream routing: 'Pass any of these as referenceImageUrl to ryla_generate_image to keep the face consistent,' which tells the agent both the purpose and the next call. It does not state explicit exclusions (e.g., what to do if no sheet exists yet, or when to prefer ryla_list_characters), so it falls short of a full when/when-not treatment.

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