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

No annotations, so the description carries the full load. It does disclose the important state effect — the session persists under this key 'from then on' — but says nothing about validation failures, what happens to an already-adopted key (override? error?), or whether the key material is retained/exposed.

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?

A single dense sentence where every clause adds information: source, format, session effect, follow-up call. Structure is slightly awkward (parenthetical provenance interrupts the main clause), but there is no padding.

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?

Given no output schema and no annotations, the description covers the essentials an agent needs: where the key comes from, its serialization format, and the persistent session consequence. Omissions are around edge cases (addr, invalid keys) rather than the primary call path.

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 0% on a nested object, so the description must compensate. It usefully specifies the format ('JSON Web Keys, P-256') and that the key must be passed 'as kept' rather than regenerated, but it omits the schema's third property 'addr' and never explains the pub/priv split beyond restating the field names.

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 action — the session adopts the supplied keypair as its operating identity 'from then on' — and ties it to two named siblings (whoami as the key source, enter as the follow-up step). The verb 'act under' is domain jargon, but the identity-switching intent is recoverable.

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?

Gives explicit provenance for the input ('from whoami { export: true } ... or the SDK's key file') and an explicit sequencing instruction: 'call enter again to go on the wire under it.' It stops short of stating when this is unnecessary or what the alternative is if a session key already exists.

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