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

Annotations only declare the safety envelope (readOnlyHint=false, openWorldHint=true, idempotentHint=false, destructiveHint=false); the description adds that it performs an OAuth initiation, returns authorize_url and state, and requires an out-of-band user browser action before proceeding. That is real behavioral context beyond the annotations, though it doesn't state that repeated calls yield fresh state values or the lifetime of the returned state.

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?

Purpose and the disambiguating 'not a Flow account' caveat are front-loaded in the first sentence, followed by a compact, ordered next-step paragraph. Every sentence carries information an agent needs to drive the flow; nothing is padding.

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?

With no output schema, the description correctly compensates by naming the return values (authorize_url, state) and describing the full two-step handoff to the user and back into add_antigravity_submit. An agent has everything required to drive this tool and its follow-up 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?

Zero input parameters, so the baseline is 4. The description does supply the meaning of the state value that must be threaded into the follow-up add_antigravity_submit call, which is useful even though this tool itself takes no arguments.

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?

Names a specific verb+resource ('Begin connecting a Google ANTIGRAVITY account') and immediately scopes it away from the crowded Flow-account siblings ('not a Google Flow account') and disambiguates from Claude/Gemini model options. An agent can tell this is the OAuth initiation step for the antigravity credential flow without opening any schema.

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 sequences the workflow: call this to begin, hand the user next_step wording plus the URL, have them sign in and press Accept, collect the code=... value from the callback page, then call add_antigravity_submit(code, state). The next tool is named with its exact arguments, so routing is unambiguous.

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