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

Annotations provide readOnlyHint=true, idempotentHint=true, and destructiveHint=false, indicating no side effects and safe retry. The description adds the fact that it returns fund instructions after data_session_open, which is behavioral context beyond annotations, but it does not mention any limitations (e.g., session must be active) or the exact return format.

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 one concise sentence with clear front-loading of the tool's purpose, and it includes a helpful example. No unnecessary words; each clause adds value.

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 (1 param) and annotations cover safety, but the description does not fully clarify the relationship with sibling tools (fund/attach) or the expected output beyond 'fund instructions.' Given the complexity of the data session workflow, more guidance would improve completeness.

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%, so the session_id parameter is already documented in the schema. The description does not add extra meaning about parameters beyond what the schema states, but the schema fully covers the parameter. Baseline 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 states a specific action: buying per-query access to a data listing, with a concrete example listing and price. It differentiates from siblings by mentioning data_preview (free taste) and data_session_open (returned fund instructions), but does not clearly distinguish from data_session_fund or data_session_attach_escrow, which are close alternatives.

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?

It implies usage context: buy access after preview and before querying, and it routes to data_preview for a free sample. However, it does not explicitly state when to use this tool instead of data_session_fund or data_session_attach_escrow, leaving the choice ambiguous.

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