session_storage

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

Annotations already declare readOnlyHint: true, and the description reinforces this with 'Snapshot', which implies no mutation. The description adds valuable behavioral context: the exact data returned (url, local_storage, session_storage), its purpose in restoring login state, and a timing constraint (before idle). No contradiction with annotations.

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 that are information-dense and free of redundancy. It front-loads the main action and return shape, then provides the use case and a timing note. Each clause earns its place, though it could be slightly shorter without losing critical context.

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?

Given there is no output schema, the description compensates by specifying the return fields. It also explains the intended workflow (session_create) and why the tool matters. While it doesn't cover edge cases like empty storage or error conditions, for a simple read-only snapshot tool this is sufficient for an agent to invoke it 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?

The input schema has a single parameter 'session_id' with 100% coverage (description: 'Session ID'). The tool description does not add any additional meaning or constraints for this parameter beyond what the schema provides. Per the baseline rule for high schema coverage, a score of 3 is appropriate.

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 uses a specific verb 'Snapshot' and clearly identifies the resource (localStorage/sessionStorage for the current origin). It also specifies the return shape {url, local_storage, session_storage}, which makes the tool's function unambiguous and distinct from generic session tools like session_state or session_export.

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 concrete usage guidance: feed the result back via session_create's 'storage' field to restore a logged-in state, and call it before the session idles out. It also explains why it's needed (cookies can't carry this half of login state). It doesn't explicitly mention alternatives or exclusions, but the use case is well-defined.

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