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

Annotations already expose readOnlyHint, idempotentHint, and openWorldHint, and the description adds useful operational context: it is a free hosted read requiring no x402 and no signer key exposure. There is no contradiction with annotations, and for a zero-argument read tool this is sufficient behavioral clarity.

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 core purpose and call guidance are front-loaded, but the description carries extra material: the 'Backpack symbols' aside is not clearly necessary for a zero-argument tool, and the generic SAP execution guidance is duplicated the input schema. It is structured but slightly padded.

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 zero-argument, read-only tool with an output schema, the description supplies enough context: what is listed, example values, no inputs, free execution, and safety boundaries. Nothing critical needs to be added.

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 tool has zero parameters and the input schema reports 100% coverage, so there is little semantic work for the description to do. It still explicitly says 'No arguments,' which removes any uncertainty for the agent.

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 opens with a specific action and resource: 'List Backpack market sessions' and gives concrete session examples (US_EQUITIES_PRE_MARKET, REGULAR, POST_MARKET, OVERNIGHT). This clearly distinguishes the tool from sibling get_markets/get_market tools, which are about market data rather than session availability.

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 gives clear call context—'No arguments. Free read'—and implies use for session discovery. However, it never explicitly states when to prefer this tool over the many sap_backpack_get_* siblings, nor does it name alternatives or exclusions.

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