invariance_session_get

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

Annotations already declare readOnlyHint=true, so the read-only nature is covered. The description adds value by specifying the fields returned (source, timestamps, attached run/agent, metadata), which is useful behavioral context beyond the annotation. No side effects are implied, consistent with a fetch operation.

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?

A single, front-loaded sentence that states the action and resource immediately, with no redundant words. Every phrase ('including its source, timestamps, attached run/agent, and metadata') adds useful information.

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 read-only fetch with one parameter and no output schema, the description is complete. It tells the agent what the tool does, what it returns, and implicitly that no side effects occur. Nothing essential is missing 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 100%: the id parameter is described as 'Session ID.' The tool description does not add additional meaning about the parameter, so it meets the baseline for fully covered schema parameters.

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 specific verb ('Fetch') and a precise resource ('a single agent-session by ID'), and enumerates the returned content (source, timestamps, attached run/agent, metadata). It clearly distinguishes from sibling tools like invariance_session_list, which retrieves multiple sessions.

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 context is clear: use when you have a session ID and need its full details. It does not explicitly state when not to use it or name alternatives, but the verb and resource make the intended use obvious, and no exclusions are needed.

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