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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive), and the description adds genuinely new context: the guide is only populated 'once it is ready', inSync applies specifically to Drive sources, and content: true can return very long text. It does not mention pagination or truncation on the long-text path, which is the one remaining gap.

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?

Front-loaded with the resource and what is returned, followed by the routing hint and the endpoint. Dense but not padded; it is a single long sentence with a parenthetical, so it reads slightly run-on without any wasted clauses.

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 carries the return-value burden and does so by naming the fields returned (title, kind, status, word count, guide topics, inSync). Combined with the safety annotations and full parameter coverage, an agent has everything needed to call this 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 coverage is 100%, so both parameters are already documented, but the description adds value the schema does not: it implies the default response is metadata-only and explains that the content flag yields 'the full text Google indexed (can be long)', flagging a size/cost consideration the schema omits.

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 ('Read one source') and enumerates exactly what comes back: title, kind, status, word count, guide, inSync, and optional full text. It also names the sibling it is not (notebook_search_sources), so an agent can distinguish it 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 routes the agent elsewhere for the adjacent use case: 'To find passages matching a query use notebook_search_sources instead.' It also states the condition that changes behavior (content: true), so both the when and the how are unambiguous.

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