create_session

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

No annotations are provided, so the description carries full burden. It discloses that the 'description' parameter does not affect execution, which is transparent. However, it does not mention potential side effects (e.g., overriding existing sessions), required permissions, or error handling. For a tool that creates resources, some behavioral details are missing.

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 concise: a short opening sentence followed by bullet-like parameter explanations. Each word adds value. It is front-loaded with the core purpose. No unnecessary repetition or verbose phrasing.

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 simple creation tool with no output schema and no annotations, the description covers the purpose, parameter meanings, and a usage rationale. It does not describe return values or possible errors, but given the tool's simplicity, it is largely complete for an agent to use correctly.

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 only 33% (only the 'description' parameter has a schema description). The tool description adds meaningful semantics for all three parameters: 'session_id' as a stable identifier, 'cwd' as the working directory, and reiterates that 'description' is free-form. This compensates well for the low schema coverage.

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 'Create a PTY session with an explicit working directory.' The verb 'create' and resource 'PTY session' are specific. It distinguishes from siblings which handle other session operations like clearing, configuring, or sending text.

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 description explains why the 'cwd' parameter is required due to MCP lacking a standard field for the client's current working directory. This provides context for when to use this tool. However, it does not explicitly state when not to use it or mention alternative tools for related tasks.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.