s3_head_object

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the read-only safety profile is established. The description adds value beyond those by disclosing that the operation returns metadata only and by listing the response fields (content type, size, last modified, ETag, custom metadata), which is genuinely useful given there is no output schema.

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 with zero filler: the core purpose and differentiator are front-loaded in the first sentence, and the response summary follows directly. Every clause earns its place.

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 simple metadata-retrieval tool with rich annotations and fully documented parameters, the description is nearly complete, and it partially compensates for the missing output schema by enumerating the returned metadata fields. Minor gaps remain around failure behavior (e.g., 404 for a missing object) and versionId semantics, but these are not blocking for correct invocation.

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 100% — bucket, key, and versionId each already carry descriptive entries, so the baseline 3 applies. The description adds no parameter-specific detail, but none is required given that the schema does the heavy lifting.

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?

States a specific verb and resource ('Get metadata for a B2 object') and the key differentiator 'without downloading it', which distinguishes it from s3_get_object and s3_head_bucket. The second sentence enumerates the response contents, making the tool's scope 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 phrase 'without downloading it' provides clear context for when to choose this tool over the object-download sibling: when only metadata is needed and the body is not. However, no alternative is named explicitly and no exclusionary conditions are stated, so it stops short of the strongest routing guidance.

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