head_objectRetrieve metadata for an S3 object in ArvanCloud storage without downloading its contents, enabling checks for existence, size, and content type.
[READ] S3 HeadObject (FA SDK head-object).
| Name | Required | Description | Default |
|---|---|---|---|
| key | Yes | ||
| bucket | Yes |
Changes observed during successful MCP inspections.
v0.5.3Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint=true and openWorldHint=true, and the description's '[READ]' prefix merely restates that. It adds nothing beyond annotations: no mention of what is returned (headers/metadata, not content), no error behavior for a missing bucket/key, and no authorization context.
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 compact sentence-fragment with no filler, so it wastes little space, but the brevity comes at the cost of clarity rather than being front-loaded informative 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?
For a two-parameter tool with 0% schema coverage, no output schema, and no annotations covering returns, the description should at minimum explain the bucket/key inputs and the metadata-only return. It does none of this, leaving the definition substantially incomplete.
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% and both required parameters (bucket, key) are undocumented in the schema. The description supplies no meaning, format, or constraint for either, leaving the two most essential inputs entirely unexplained.
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 operation (S3 HeadObject) and the underlying SDK call, and the [READ] tag signals it is a read. However, it never states in plain terms that this retrieves an object's metadata/headers without downloading the body, which is the actual behavior an agent needs to distinguish it from get_object_text or list_objects.
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 when-to-use guidance and no mention of alternatives such as get_object_text (to read content) or list_objects (to enumerate keys), even though those siblings exist. An agent must infer the choice purely from the tool name.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.