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

Beyond the annotations (readOnlyHint, idempotentHint, etc.), the description adds meaningful behavioral context: it is a free read (no payment required), advises calling directly without x402, and clarifies the signer boundary (hosted reads never receive keypair bytes; value-moving results must be finalized locally). These details are not present in the annotations and help the agent understand operational constraints. It does not contradict 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 tool-specific portion is concise: a clear first sentence and symbol examples. However, the description includes a lengthy 'SAP MCP execution guidance' paragraph that is duplicated verbatim in the input schema's description. This redundancy makes the description longer than necessary and dilutes the tool-specific content. The structure is acceptable but not optimal for skimming.

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 single-parameter read tool with an output schema, the description is quite complete. It states exactly what data is returned (mark price, index price, funding rate, next funding timestamp), clarifies symbol types, and provides pricing/routing guidance. The presence of an output schema reduces the need to detail return format. The only minor omission is explicit rate-limit or error-handling notes, but these are not critical for a read-only tool.

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 already describes the single 'symbol' parameter as a 'Perp market symbol' with an example. The description enriches this by explaining the broader symbol formats (spot, perp, stock, RFQ) and reiterating examples, which helps the agent construct valid symbols beyond the schema's terse description. This adds meaning to the parameter beyond the schema's own coverage (100%), so a score above baseline 3 is warranted.

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 retrieves Backpack mark price, index price, funding rate, and next funding timestamp for a PERP symbol, with a concrete example (SOL_USDC_PERP). It also distinguishes its scope from other market types by listing spot, perp, and stock symbol conventions, though it focuses on PERP. This leaves no ambiguity about the tool's function.

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 minimal guidance on when to use this tool over alternatives. It mentions 'Intent: read/discovery workflow' and 'Free read' but does not explicitly compare to sibling tools like sap_backpack_get_ticker or sap_backpack_get_markets. The only implicit differentiator is the PERP-specific focus, which is not framed as a choice criterion. No when-not-to-use or alternative tool recommendations are given.

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