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

Annotations only indicate non-read-only and non-destructive. The description adds that the block is created at its defaults and gets a fresh id, plus a follow-up workflow (update_screen). This is valuable behavioral context beyond the minimal annotations, though it doesn't discuss side effects or permission requirements.

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?

Two sentences, front-loaded with the core action and purpose, then the key contrast with update_screen. No wasted words; every clause earns its place.

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 simple 3-parameter tool with an output schema, the description fully covers the what, when, and how it fits into the workflow. An agent has enough to decide and call it correctly.

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 100%—each parameter already has a detailed description, including the type enum and mentions of 'at its defaults'. The description reinforces this but adds no new parameter-specific information. Baseline 3 applies.

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?

Clear statement of action ('Appends one block'), the resource (a screen), and a distinctive trait (with a fresh id). It contrasts with update_screen (restate whole screen) and implicitly distinguishes from add_screen, so an agent can tell them apart without opening schemas.

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?

Explicitly describes when to use this tool ('the quick path when you only want to add something') versus when not (rather than restate the whole screen), and names the alternative (update_screen). No ambiguity about the intended context.

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