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

With only a title annotation, the description carries the behavioral burden. It discloses that apps run in a sandbox, that direct external fetch is blocked, and that internal calls must use fetch or mu.service, which are important constraints for producing valid app HTML. It does not disclose the create operation's own behavior, such as idempotency, validation, or response format, leaving some 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?

The description is dense but all sentences add value: creation purpose, apps_build alternative, sandbox constraints, and coding cautions. The lack of punctuation between 'from a description' and 'Apps run' makes it feel run-on, but information is front-loaded with the primary 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?

For a create tool with 9 parameters and no output schema, the description provides good environmental context and identifies the key sibling, but it omits what the call returns and how creation is confirmed. The guidance about inspecting service schemas is useful for writing the HTML, but the create API's own response and error behavior remain unspecified.

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?

All 9 parameters have schema descriptions, and the description adds little beyond confirming that HTML is the input ('Takes the HTML'). It does not elaborate on slug derivation, price limits, or visibility toggles beyond what the schema already says. Baseline 3 applies at 100% schema coverage.

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 and resource ('Create an app') and describes the artifact as a small, self-contained HTML tool hosted here. It also distinguishes itself from apps_build by noting that apps_build writes the app from a description, whereas this tool takes the HTML. The purpose is unambiguous despite the slightly run-on sentence.

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?

The description signals the main alternative: apps_build writes the app from a description, so apps_create is for when you already have HTML. It also provides sandbox constraints that shape how the HTML should be written. However, it does not explicitly say 'use apps_build when you lack HTML' or enumerate when to avoid apps_create, relying on implication.

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