update_index

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

With no annotations, the description carries the full burden for behavioral disclosure. It explicitly states 'Create or overwrite,' which clearly warns of mutation and potential destruction of existing content. It also adds useful detail about frontmatter exceptions. However, it doesn't disclose other potential side effects like directory creation, permissions, or idempotency, leaving some behavioral gaps.

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 concise and well-structured. The first sentence delivers the core purpose. The second paragraph provides necessary context about index file format and a spec reference. Every sentence earns its place, and there is no redundant or filler content.

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 has an output schema, so return values need not be explained. The description gives some context about index file formatting and references a spec. However, it does not address the relationship to the 'generate_index' sibling, which is a notable gap given the tool's role as a manual alternative. The description is functional but not fully complete in guiding correct usage.

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%, and both 'path' and 'content' have clear descriptions in the schema. The description adds no additional semantic meaning for parameters beyond what the schema already provides. Per the rubric, baseline is 3, and the description doesn't go beyond that.

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 ('Create or overwrite') and resource ('an index.md file for a directory'). It explains what index files are for ('list the directory's concepts for progressive disclosure'). However, it doesn't explicitly distinguish this from the sibling 'generate_index' tool, so it misses the top score for sibling differentiation.

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 gives no guidance on when to use this tool versus alternatives. It doesn't mention that 'generate_index' might be a better choice for automatic generation, nor does it state any exclusions or prerequisites. The implied usage is 'when you need to create or overwrite an index manually,' but no explicit guidance is provided.

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