Retrieve an email attachment as raw base64 data using its message ID and attachment ID, so agents can download or process files from Gmail messages.
Fetch the raw base64 data for an attachment on a message.
| Name | Required | Description | Default |
|---|---|---|---|
| user_id | No | ||
| message_id | Yes | ||
| attachment_id | Yes |
| Name | Required | Description | Default |
|---|---|---|---|
| size | No | ||
| message_id | Yes | ||
| data_base64 | Yes | ||
| attachment_id | Yes |
Changes observed during successful MCP inspections.
v0.1.1Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description bears full responsibility. It only states it fetches raw base64 data, but omits any behavioral context like authorization requirements, rate limits, error handling for missing attachments, or size limits.
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 a single efficient sentence with no filler. However, some additional detail (e.g., a note on parameter usage) could be added without significant bloat, so it is not maximally concise for the information needed.
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?
Despite having an output schema (so return values are covered elsewhere), the description lacks critical context: no mention of how to obtain attachment_id or message_id, and no usage guidance. For a simple fetch tool, it is minimally complete but leaves gaps.
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%, yet the description adds no meaning to the parameters (user_id, message_id, attachment_id). It fails to explain what each parameter represents or how to obtain them, leaving the agent to infer solely from parameter 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?
The description clearly states the verb ('Fetch'), the resource ('attachment'), and the format ('raw base64 data'), making it specific and distinguishable from sibling tools like gmail_add_attachment or gmail_remove_attachment. It fully explains what the tool does.
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?
No guidance on when to use this tool versus alternatives such as gmail_get_attachment or other attachment-related tools. No context on prerequisites (e.g., message must be opened) or when not to use it.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.