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

Annotations already provide readOnlyHint=true, and the description adds behavioral context by explaining that events sharing a sessionId belong to the same visit and that one visit can fetch several files. This goes beyond the annotations and helps the agent interpret the response structure.

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?

Three short sentences carry all necessary information concisely. The purpose is front-loaded with the question answers, and the sessionId grouping note is included without any 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?

For a tool with one simple parameter and no output schema, the description adequately explains the return concept (download events with timestamps, per-recipient status, sessionId grouping). However, it omits explicit parameter semantics and any mention of prerequisites or edge cases, leaving some ambiguity about how to target a specific transfer.

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 0%, so the description must compensate for the undocumented 'id' parameter. However, it never explicitly states that 'id' refers to the transfer identifier; it only implies it via 'did the client download it?'. This is a meaningful gap that could cause incorrect invocation.

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 states a specific verb+resource: it returns download events for a transfer, with timestamps and per-recipient status. It clearly differentiates itself from sibling tools like get_transfer and list_transfers by focusing on download receipts and the sessionId grouping concept.

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 frames usage as answering 'did the client download it? when? how many times?', which gives clear context for when this tool is appropriate. It does not explicitly exclude alternatives or mention when not to use it, but the purpose itself largely defines the use case.

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