open_collection

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

Annotations already indicate idempotentHint=true and readOnlyHint=false, so the tool is idempotent and may involve state changes. The description adds behavioral context: caching for subsequent operations, prerequisite that the collection was created with create_and_open, and that it returns success/error messages. It does not contradict annotations, which is good, and provides additional detail beyond the annotations.

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: a brief intro, clearly labeled Args and Returns sections, and concise examples. Every sentence serves a purpose with no redundant information, achieving a high signal-to-noise ratio.

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's simplicity (open an existing collection) and the presence of an output schema, the description is complete. It covers the prerequisite, caching behavior, and error conditions, leaving no significant gaps for an AI agent to understand what the tool does and how to use 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?

Although the input schema already has descriptions for each property (e.g., 'path', 'collection_name', 'read_only'), the description adds value by summarizing the parameters contextually and giving example usage. However, since schema coverage is effectively high (descriptions exist in schema), the description's contribution is moderate but helpful.

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 'Open an existing Zvec collection from disk,' specifying the verb (open) and resource (existing Zvec collection). It distinguishes from sibling tool create_and_open_collection by emphasizing 'existing' and referencing the creation tool, making the purpose unambiguous.

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 explicit usage instructions with 'Use when' and 'Don't use when' examples, including a direct alternative mention: 'Don't use when: Collection doesn't exist (use create_and_open_collection).' This gives clear context for when to invoke this tool versus alternatives.

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