download_attachmentDownload an attachment file by its ID to retrieve its content encoded in base64.
Download an attachment file by its id. Returns the file base64-encoded. Read.
| Name | Required | Description | Default |
|---|---|---|---|
| account | No | Which configured FastBound account to use for this one call — an alias or account number (see list_accounts). Omit to use the active account. | |
| attachmentId | Yes | GUID of the attachment. |
Changes observed during successful MCP inspections.
v0.2.0Input schema / properties / accountAdded value: +{
+ "description": "Which configured FastBound account to use for this one call — an alias or account number (see list_accounts). Omit to use the active account.",
+ "type": "string"
+}v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint and openWorldHint, so the read-only safety profile is covered. The description adds the otherwise-missing output behavior (base64 encoding), which is valuable 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?
Three terse sentences, front-loaded with the core behavior, and no filler. 'Read.' is short and reinforces the safety profile without wasting space.
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?
The tool is simple, the schema fully covers parameters, and annotations cover safety. The missing output schema makes the base64 return note important; the only small gap is the lack of any mention of error/failure behavior, which is not essential for basic use.
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 description adds no parameter meaning beyond 'by its id,' while the schema already documents both attachmentId and account at 100% coverage. Baseline 3 is appropriate because the schema carries the parameter documentation burden.
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 operation ('Download an attachment file by its id') and clearly identifies the resource. It is easily distinguished from report-download siblings like download_bound_book and download_4473 by resource type.
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?
Provides no explicit when-to-use guidance, prerequisites, or alternatives. 'Read.' hints at safe invocation but does not explain when to choose this tool over other download tools or how to obtain an attachmentId.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.