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

readOnlyHint=true is already supplied by annotations and is consistent with the description. The description does add useful non-schema context in '1 unit', disclosing the cost of the call. It says nothing about failure behavior when the upstream tool name is unknown or the upstream is unreachable.

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 short fragments with no wasted words, and the resource is front-loaded. It is arguably too terse rather than too long, but per the conciseness criterion it earns its place.

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 read-only lookup with a fully described schema and no output schema, the core intent and cost are covered. The missing piece is how it relates to the invocation sibling and what happens on invalid upstream names, which matters for an agent planning a call sequence.

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 all three parameters (name, apiKey, upstream) are already documented in the schema. The description adds no additional syntax, format, or defaults beyond that, so the baseline 3 applies.

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 phrase 'Full input schema of an upstream tool' names a specific resource and result, and 'schema' distinguishes it reasonably well from slim_call and slim_index. However, it is a bare noun phrase with no verb, so the action (fetch/retrieve) is only implied rather than stated.

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?

There is no guidance on when to call this versus a sibling like slim_call, nor any stated prerequisite or follow-up step. The likely workflow (fetch the schema first, then invoke via slim_call) must be inferred entirely by the agent.

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