s3_get_presigned_url

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

Beyond the annotations, the description adds valuable behavioral context: the URL is a bearer capability, it is short-lived, it should be treated as sensitive until expiry, and B2 does not support presigned POST. The destructive nature of PutObject URLs is consistent with destructiveHint=true, and readOnlyHint=false matches the upload capability. No contradiction exists.

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 sentences, each earning its place: the core behavior, the operational advantage and sensitivity guidance, and the critical B2 limitation. The most important information is front-loaded, with no filler or redundancy.

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 no output schema, the description usefully states that the response includes URL, operation, expiresIn, and expiresAt. It also covers the key operational context (direct byte flow, sensitivity, unsupported POST flow) and the tool's role relative to siblings. An agent has enough information to call this tool correctly and interpret its result.

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 input schema provides 100% coverage of all seven parameters, including descriptions, defaults, enums, and constraints, so the description does not need to restate parameter details. The description does add contextual meaning by labeling the URL a bearer capability and mentioning the response fields, but this is not parameter-level semantics. Baseline 3 is appropriate.

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 names a specific verb (Generate), a precise resource (short-lived presigned URL bearer capability for one B2 object), and the two allowed operations (GetObject download / PutObject upload). It also distinguishes itself from sibling tools by explaining that bytes flow directly between client and B2 and never through the MCP server.

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 clearly positions this as 'the preferred path for moving real object data,' giving the agent a direct criterion for choosing it over s3_get_object or s3_put_object. It also explicitly warns that presigned POST is unsupported and instructs to use a PutObject URL instead, but it does not enumerate other alternative tools or when to avoid this tool.

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