Get Active File

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

Annotations already provide readOnlyHint and idempotentHint, but the description adds valuable behavioral context: the Local REST API plugin requirement, the needed environment variables, and the fact that it targets the live Obsidian vault process. This goes beyond the structured annotations without contradicting them.

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 compact and front-loaded with the core behavior. Each sentence adds a distinct fact: what it returns, that it is read-only, the plugin prerequisite, the intended usage, and the vault.select caveat. The only small redundancy is repeating 'read-only,' but it is minimal and reinforces a key safety signal.

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?

For a zero-parameter tool with full annotation coverage and an output schema, the description is complete: it covers prerequisites, return fields, usage intent, and the routing caveat. Nothing an agent needs to decide whether or how to call this tool is missing.

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 and the input schema is fully descriptive with additionalProperties false, so the baseline for this dimension is 4. There is no parameter detail needed, and the description appropriately does not invent any.

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 starts with a specific verb ('Return information') and names the exact resource: the file currently open and focused in Obsidian. It enumerates the returned fields (path, modification time, edit/preview mode) and the read-only nature clearly separates it from mutation siblings like workspace.openFile and workspace.closeActiveFile.

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?

It gives explicit usage context: use this to orient the agent before other workspace-level mutations. It also clarifies a potential routing confusion with vault.select, stating that vault.select does not affect this tool and only changes filesystem-tool routing, which serves as a clear when-not/alternative guideline.

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