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

Annotations already declare readOnlyHint=true, destructiveHint=false, idempotentHint=true. Description adds valuable behavioral details: files are scoped to the authenticated agent, non-owned names return NOT_FOUND, and existence is never leaked (security guarantee). Requires authentication. No contradictions.

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, front-loaded with the primary action. Every sentence adds value: first for purpose and return content, second for scope, error, and security. No redundancy or fluff.

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 (one parameter, output schema exists), the description covers purpose, scope, error behavior, and authentication. Does not mention file size limits or encoding, but these are minor. Adequately complete for safe 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?

Only one parameter (filename) with 100% schema coverage including an example. The description just says 'by name', adding no additional meaning. Baseline 3 is appropriate since the schema already provides sufficient clarity.

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?

Clearly states the verb 'Download' and the resource 'vault files by name', and clarifies it returns both content and metadata. Differentiates from siblings like vault_list_files (list), vault_search_files (search), vault_move_file (move), etc., making the tool's specific function 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?

Provides clear context: use to download your own files by name. Mentions scoping (files are agent-specific) and error behavior (NOT_FOUND for non-owned names). Does not explicitly list alternatives or when not to use, but the context is strong enough to guide selection among siblings.

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