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

Beyond the annotations (which only say it is not read-only, not idempotent, not destructive), the description discloses the full lifecycle: uploads are kept until keep_character or one day, a paid sheet for 30 days, photos of other people are 'set aside', a base outfit line is generated, and generation is priced in credits while add is free. This is exactly the extra behavioral context annotations cannot convey.

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?

Content density is high and the main purpose is front-loaded, but the text is a single run-on block of parenthetical clauses that is hard to scan; splitting mode generate and mode add into discrete lines would materially improve it without losing information.

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 three-parameter mutation with no output schema, the description covers costs, retention windows, required plan and storage, error codes, and follow-up tools. An agent has everything needed to call it correctly and interpret failures.

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%, so the baseline is 3, but the description adds real meaning: the photo set must be one person from any angles, a clear face is required, and generate is credit-priced while add is free. It also notes the CLI upload alternative to URL parameters. It stops short of clarifying what happens on invalid face checks.

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 names a specific action and its two variants: it takes '1 to 5 photos of one person' to draw a sheet, or 'one finished sheet' to add as-is. An agent can distinguish the two modes without opening the schema, though the phrasing is convoluted ('mode add: one finished sheet') and takes effort to parse.

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 explicitly routes between modes ('mode generate' vs 'mode add'), names the downstream/related siblings an agent will need (draw_character_sheet, keep_character, list_character_requests, get_account), and states preconditions and the error codes that signal them (402 plan_required, 402 storage_full). This is unusually complete when-to-use guidance.

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