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

Annotations declare readOnlyHint=false, idempotentHint=true and destructiveHint=false; the description usefully explains what that non-read-only side effect is ('can save the original as a reusable asset') and rules out the two things an agent would most fear ('does not generate or charge'). It stops short of stating permissions, failure behavior, or whether the save always occurs ('can save' is hedged).

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, front-loaded with the return value and followed by parameter rules and side-effect caveats; nothing is padding. The phrase 'can save the original as a reusable asset' is slightly vague about whether the save is conditional, which costs a point.

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?

For a two-parameter tool with no output schema and no schema descriptions, the description covers the return value, both parameters' semantics, the downstream usage of the result, and the side-effect/charging profile. Remaining gaps are edge-case behavior (invalid or unowned IDs) rather than anything blocking correct invocation.

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 0%, so the description carries the full burden, and it does add real meaning: characterId must be an exact ID obtained from get_saved_character, and lookId is optional with a clear condition for omitting it. It does not restate the numeric-string pattern or what happens with a malformed or non-owned ID.

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 states a specific verb and output ('Return the owned original image asset ID') scoped to an exact characterId and optional lookId, and ties the source to the sibling get_saved_character. It is clearly a resolver rather than a mutation or listing tool, though the exact boundary with get_saved_character could be spelled out more sharply.

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 an explicit conditional rule for the optional parameter ('Omit lookId only when the user chose the base identity') and a downstream instruction ('Keep the returned asset ID for downstream reference slots'). There is no explicit when-not-to-use or statement of alternatives beyond the implied dependency on get_saved_character.

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