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

Annotations already indicate this is not read-only and not destructive. The description adds useful context beyond that: the new session records the original as its source and is editable. It reinforces the non-destructive nature ('source is never modified'). While it doesn't detail side effects like permissions or output, the annotation coverage lowers the burden, and this is adequate for a simple mutation tool.

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?

Two sentences, no wasted words. It front-loads the primary action, then clarifies the key safety guarantee (source never modified) and gives a usage hint. Every sentence contributes directly to the agent's understanding.

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 (one parameter, no output schema), and the description covers what it does, when to use it, and the key side-effect guarantee. It doesn't explicitly describe the return value, which could be a gap since there's no output schema, but the phrase 'into a new editable session' strongly implies the result. For this complexity level, it is complete enough 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?

The schema already provides 100% parameter coverage with a thorough description of session_id (UUID format, what to pass, what not to pass). The tool description adds minimal extra meaning beyond calling it an 'existing session,' which is already implied by the schema. Per the rubric, high schema coverage sets a baseline of 3, and there is no compensatory detail in the description.

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 copies an existing session into a new editable one, with a specific verb (copy), resource (session), and outcome. It also mentions the source is never modified, distinguishing it from sibling tools like edit_session (which implies in-place editing) and create_session (which likely creates from scratch). The phrase 'this is how to continue from published work' further clarifies its unique role.

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 clear context for when to use the tool: 'this is how to continue from published work.' It implicitly contrasts with other actions like publishing or editing, and emphasizes that the source is left untouched. However, it does not explicitly name sibling tools or state when not to use it, so it falls short of a 5.

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