Retrieve a specific session message as parsed JSON using its basename or full S3 key, enabling direct access to message content without listing the entire session.
Fetch and parse a message JSON object.
message_key may be either a basename like message_0.json or a full S3 key.
| Name | Required | Description | Default |
|---|---|---|---|
| agent_id | No | agent_default | |
| session_id | Yes | ||
| message_key | Yes |
Changes observed during successful MCP inspections.
v0.1.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations provided, the description carries the full burden of behavioral disclosure. It mentions fetching and parsing, but does not disclose return shape, error behavior, permissions, or side effects. This is a notable gap for a tool with zero annotation support.
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 compact and front-loaded: the core action appears first, followed by a single useful parameter clarification. Every sentence earns its place with no redundancy.
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?
Given the absence of annotations and output schema, the description leaves important context undeclared: expected return value, failure modes, and how this tool relates to sibling getters. It is adequate for a simple call but not complete enough for reliable autonomous selection and 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?
The description adds valuable meaning for message_key by clarifying it can be a basename or full S3 key. However, session_id and agent_id remain explained only by their names, and with 0% schema description coverage, the description does not compensate enough for the missing parameter details.
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 states a clear verb ('Fetch and parse') and a specific resource ('message JSON object'), which identifies what the tool operates on. It doesn't explicitly contrast with sibling tools, but the resource type is specific enough to distinguish it from sessions_get_session_json or sessions_get_agent_json.
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 like sessions_get_raw or sessions_list_messages. The only usage-related hint is the message_key format, which is parameter guidance rather than tool-selection guidance.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.