Acquire session

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

Annotations already declare readOnlyHint=false, idempotentHint=true, and destructiveHint=false. The description adds genuine behavioural context beyond that: it never spends money, it adds to a private library, and a paid listing yields status=payment_required with price and listing URL. It does not explain idempotent re-acquire behaviour, but the annotation covers that.

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?

Two sentences, zero filler, with the entitlement scope front-loaded and the no-purchase guarantee immediately after. Every clause carries decision-relevant 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?

There is no output schema, and the description usefully foreshadows the paid-listing response shape (status=payment_required, price, listing URL). For a low-risk, annotated mutation with one required param, this is nearly complete; only the success-path result and the version parameter's meaning are unstated.

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 coverage is 67% – id and tenant carry descriptions, version has only a default of 'latest'. The description adds no parameter-level meaning at all (no syntax, no source guidance), so it neither compensates for the gap nor improves on the schema. Baseline 3 for a mostly-documented schema.

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?

Names a specific verb+resource ('Add a marketplace session ... to your private library') and scopes it by entitlement (free, bought, granted). An agent can distinguish this from search_sessions, publish_session, and the purchase-related siblings without opening any schema.

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?

States the qualifying condition clearly ('sessions you are entitled to') and rules out the paid case ('Never buys anything ... returns status=payment_required'). It gives clear context for when this is the right tool, but never names the alternative an agent should reach for instead (e.g. request_purchase), so the routing guidance is inferential rather than explicit.

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