NEXO Brain

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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It mentions the tool lists directories but doesn't specify output format, pagination, permissions required, or potential side effects (e.g., read-only nature). This leaves gaps in understanding the tool's behavior beyond its basic function.

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?

The description is a single, efficient sentence that directly states the tool's purpose without unnecessary words. It is front-loaded and wastes no space, making it easy to understand at a glance while conveying essential information about the resource and scope.

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?

Given the tool has no parameters, an output schema exists, and annotations are absent, the description is moderately complete. It specifies what is listed (directories indexed by FTS5) and the types (builtin + dynamic), but lacks behavioral details like output format or usage context, which could be important for an agent to invoke 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?

The tool has 0 parameters with 100% schema description coverage, so no parameter details are needed. The description appropriately omits parameter information, as the schema fully covers the input structure. This aligns with the baseline for tools with no parameters, where minimal description suffices.

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 the tool's purpose with a specific verb ('List') and resource ('directories being indexed by FTS5'), and distinguishes between 'builtin + dynamic' types. However, it doesn't explicitly differentiate from sibling tools like 'nexo_index_add_dir' or 'nexo_index_remove_dir', which are related to index management but serve different functions.

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 no guidance on when to use this tool versus alternatives, such as how it differs from other index-related tools (e.g., 'nexo_index_add_dir' for adding directories). It lacks context on prerequisites or scenarios where listing indexed directories is appropriate, leaving usage unclear.

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