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

The description adds valuable context beyond the annotations: 'A new session does NOT replace or affect the existing project — earlier sessions remain available.' It clarifies the operation is non-destructive and that sessions are isolated but persistent. Annotations already indicate destructiveHint=false, but the description enriches this with specifics about project impact and session persistence. A 4 is warranted because it doesn't mention whether a project must already exist or what the new session's active status is.

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 two sentences: the first states the core purpose, the second provides usage and a behavioral caveat. Every sentence earns its place, with no redundant information or filler. It is appropriately front-loaded and easily scannable.

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 tool with two parameters and an output schema, the description is fairly complete. It covers purpose, usage, and a key behavioral guarantee. However, it doesn't explicitly state that project_id must reference an existing project (though implied by sibling create_project), nor does it mention the return value—though the output schema presumably covers that. Slightly more detail could push it to 5, but 4 is a solid score.

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 100%, with both 'project_id' and 'label' already described in the input schema. The tool description adds only minimal meaning beyond this, such as implying project_id refers to an existing project. The baseline of 3 is appropriate because the schema does the heavy lifting and the description doesn't compensate with additional parameter context.

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 tool's function: 'Create a new development session for a project — a separate conversation with its own context.' It uses a specific verb (create) and resource (development session), and distinguishes itself from sibling tools like create_project (creating a project) and chat (continuing a conversation). The phrase 'separate conversation' further clarifies its scope.

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 provides an explicit when-to-use trigger: 'Use when the user wants to start a distinct development topic.' It also implies a contrast with existing sessions by stating earlier sessions remain available. However, it doesn't explicitly name alternative tools (e.g., 'use dreamagent_chat for continuing a conversation'), so it's clear but lacks explicit exclusions.

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