get_source_guide

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

No annotations are provided, so the description carries the full burden. It does add real behavioral context beyond the name: the empty-summary case for unsummarised sources and the RPC backing. But it omits auth/permission requirements and, importantly, whether reading a not-yet-summarised source triggers or requires summarisation.

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?

Three short, front-loaded sentences with no filler; the core purpose comes first and the edge case follows. 'RPC-backed' is mildly useful but borderline noise for an agent deciding whether to call it.

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?

An output schema exists, so return-shape explanation is not needed, and the empty-result case is covered. The remaining gap is addressing: with zero required parameters, the description never says that at least one of source_id/source_name (plus a notebook identifier) must be supplied.

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%, so all four parameters (source_id, notebook_id, source_name, notebook_url) are already documented in the schema. The description adds nothing about the alternative addressing modes or which combination is actually required, so 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?

States a specific verb and resource: reads NotebookLM's own summary and key topics for a single source. The phrase 'for a single source' implicitly separates it from the notebook-level sibling get_notebook_summary, though it never names that sibling 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?

Usage is only implied by the resource scope: use it when you need per-source summary content rather than a whole-notebook summary. There is no explicit when-to-use, no prerequisites, and no mention of alternatives such as source_read or get_notebook_summary.

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