List sources

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

With no annotations, the description carries the full burden. It clearly implies a read-only listing operation and adds context about the content types and fragment counts. While it doesn't explicitly state 'read-only' or mention ordering/pagination, the behavior is transparent enough for a simple list tool.

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: the first describes functionality, the second explains the use case. No fluff, perfectly front-loaded and concise.

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?

The tool is simple with no params or output schema, and the description covers what it returns and why to use it. It doesn't detail exact return shape or ordering, but that's acceptable for a listing tool with such clear intent.

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?

The tool has zero parameters, so the baseline is 4. The description adds value by explaining the output (fragment counts), which is informative but not parameter-related.

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?

The description clearly states that the tool lists all sources the brain has read, with examples (interviews, PRDs, tickets, threads, docs) and fragment counts per source. This specific verb+resource is distinct from sibling tools like list_contradictions or list_gaps.

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 provides a clear usage context: 'Use it to see what an answer could possibly be based on before you trust one.' It does not explicitly exclude cases or name alternatives, but the intended use is evident.

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