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

Annotations already cover safety (readOnly=false, destructive=false, idempotent=false, openWorld=false), and the description adds real value beyond them: it pulls from saved setup answers with optional overrides, may also create a character, and triggers automatic navigation afterward. It stops short of saying a duplicate call creates a second project or what the response contains, which matters given idempotentHint=false.

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 sentences, front-loaded with the core action and source data, then conditional usage, then post-conditions. The closing "Then help them make the first video" is slightly extraneous to tool selection but is short and arguably useful onboarding guidance.

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 16-parameter, nested-object creation tool with no output schema, the description says nothing about the return value (project id? character id?), error behavior, or how saved answers interact with passed parameters when both exist. Annotations cover safety, but the operational picture is only partially complete.

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?

With 16 parameters and only 63% schema description coverage, the description contributes almost nothing per-parameter beyond the phrase "plus any answers you pass here." The nested `sells`, `character`, and style/voice/people relationships are documented only in the schema, so the description neither compensates for the coverage gap nor adds meaning on top of it.

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 (creates) and resource (the project) and adds the source of truth: the saved setup answers plus any answers passed here, and the character if present. That distinguishes it from update_project and create_character reasonably well, though it never names those siblings explicitly.

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?

"Use it for the first project and for more projects when the plan allows them" gives clear selection context and even surfaces the plan-limit constraint. It also describes what happens after creation (app advances to the chosen plan or into the app), but it does not state prerequisites such as setup answers needing to be saved first or what to do instead if a project already exists.

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