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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the description is free to add environment context instead — and it does, disclosing that this is testnet data and a versioned machine format. That is real value beyond the structured fields, though it says nothing about error behavior for an unknown id.

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 sentences: format/scope first, prerequisite second. Every clause carries information and nothing is 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 one-parameter read tool with full annotation coverage, the only real gap is what the return payload looks like — there is no output schema, and 'full sealed envelope' gestures at it without defining the fields. Adequate but slightly thin on the return shape.

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 100% and the schema itself already gives the 'ep.6' example, so the description's example adds nothing new. Baseline 3 applies since the schema does all the parameter work.

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?

States a specific verb and resource ('the full sealed envelope for one call id') and pins the format explicitly (wr.calls.v1, testnet), which separates it from the list-oriented siblings. It stops short of saying what a 'sealed envelope' contains, but an agent can tell this is a single-record fetch by id.

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?

'Use calls_list first if you do not have a call_id' gives an explicit prerequisite and names the alternative tool, which is exactly the guidance needed for an id-keyed getter. It omits calls_since, also a valid id source per the schema, and gives no when-not conditions, keeping it below a 5.

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