Fetch an S3 object's metadata—size, content type, ETag—without downloading it. Inspect bucket objects before reads, restores, or other actions.
Read object metadata.
| Name | Required | Description | Default |
|---|---|---|---|
| key | Yes | ||
| bucket | Yes | ||
| version_id | No |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries the full behavioral burden. It does not disclose that no object body is returned, whether permissions/403 errors are common, whether a version_id is required for non-current versions, or what metadata fields come back. Only the implied read-only nature of 'Read' is conveyed.
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?
It is a single front-loaded sentence with no filler, which is structurally clean. But brevity here tips into under-specification: the sentence is too small to carry the tool's semantics rather than genuinely efficient.
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?
With no annotations, no output schema, and 0% parameter coverage, an agent lacks everything it needs to call this correctly. Details on version_id usage, the metadata-only return, and error conditions are all missing.
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 and does not. The three parameters (bucket, key, version_id) are only inferable from their names; the description adds no meaning, format, or requirement details beyond the schema property names.
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?
'Read object metadata' names a specific verb (read) and resource (object metadata), which is clearer than a tautology. However, it does not differentiate from close siblings like s3_get_object or s3_get_object_tagging, so an agent can't tell from the text alone why HEAD-style metadata retrieval is the right pick over a full GET.
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?
There is no guidance on when to use this tool versus alternatives such as s3_get_object (content) or s3_get_object_tagging (tags). The distinction only surfaces semantically if the agent already knows S3 HEAD semantics; the description never states it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.