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

Annotations already declare readOnlyHint and idempotentHint, so the description does not need to restate them. The description adds that the URL is 'time-limited' and 'presigned,' indicating the tool does not directly return file contents but a temporary access link. This is valuable behavioral detail not covered by annotations. It does not contradict any annotation.

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 two sentences long, directly to the point, and free of extraneous details. It front-loads the core function (returning a presigned URL) and includes the usage guidance in the second sentence. The example is brief and illustrative without bloating the text.

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 output schema is provided (though not shown in the prompt, it is indicated as present), the description does not need to detail the response format. It fully covers the purpose, parameters, and usage nuance, making the tool self-sufficient for an agent to decide when and how to call it.

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 schema covers 100% of parameters with descriptions. The 'key' parameter is explained as the full object key including prefixes and filename, and 'expires' is described as the URL lifetime in seconds with a default and range constraints (60–3600). The description reinforces the key format with an example. No additional clarification is needed.

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 returns a time-limited presigned download URL for a given S3 object key. It also provides a concrete example (orderbook/kalshi/btc/15m/2026-05-21/FILE.gz), making the purpose unambiguous. It is distinct from sibling tools like get_candles_file or get_orderbook_file, which retrieve specific data files, and list_market_data, which lists available keys.

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 explicitly instructs when to use this tool: 'Use this when you already know the exact key; otherwise prefer list_market_data plus the per-endpoint file tools.' This gives clear guidance and contrasts with alternatives, leaving no ambiguity about the appropriate context.

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