Fetch stdout/stderr from a session using byte offsets, revealing true exit code, truncation, timeout, and more-output status.
Read stdout/stderr of a previously started session using byte offsets; shows true exit code, truncation, timeout and more-output status.
| Name | Required | Description | Default |
|---|---|---|---|
| offset | No | ||
| wait_ms | No | ||
| max_bytes | No | ||
| session_id | Yes |
Changes observed during successful MCP inspections.
v0.2.0-preview.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior. The description adds meaningful behavioral context by revealing that the result includes the true exit code, truncation, timeout, and more-output status, which are not visible in the schema or annotations. This goes beyond what structured data provides.
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?
One sentence with no filler. The core action is front-loaded, and the appended status details earn their place by describing output semantics an agent needs to interpret the result.
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 read tool with four parameters and no output schema, the description covers the essential return statuses and the precondition of an existing session. It does not spell out incremental offset usage or the output body format, but the byte-offset phrasing and status list are sufficient for correct 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?
Schema description coverage is 0%, so the description must compensate. It clarifies offset via 'byte offsets' and indirectly references wait_ms and max_bytes through 'timeout' and 'truncation', but does not explicitly explain wait_ms behavior or the exact role of max_bytes beyond the schema names and defaults.
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?
Description uses a specific verb ('Read') with a clear resource ('stdout/stderr of a previously started session'), and explains the byte-offset mechanism. This clearly distinguishes it from sibling tools like process_start, process_input, and process_stop, which write to or manage sessions rather than read their output.
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?
The phrase 'previously started session' establishes the precondition that a session must already exist, and reading stdout/stderr is distinct from the write-oriented process_input. It provides clear context but does not explicitly name alternatives or state when not to use this tool.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.