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

Annotations already disclose the safety profile (readOnly=false, destructive=true, idempotent=true, openWorld=true), so the bar is lower. The description adds useful context — the signature is 'optional', the claim must be 'owned' and 'historical', and arena capture snapshots/receipts are sealed — but it never explains why the operation is destructive or what changes as a result.

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 that are front-loaded with the discriminating 'Legacy compatibility' scope marker. The second sentence is somewhat cryptic but does useful work by ruling out new arena capture IDs; there is little wasted text.

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?

An output schema exists so return values need not be described, and annotations plus 100% schema coverage carry most of the burden. However, for a destructive, open-world signing tool the relationship to the takeover workflow (submit_takeover, start_takeover_challenge, get_root_signing_payload) is never clarified, leaving the agent to guess how this fits in the 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 four parameters are already documented in the schema, including the legacy claim_id versus capture-ID distinction. The description adds no parameter-level detail beyond what the schema provides, making the baseline 3 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?

States a specific action (attach an Ed25519 signature) on a specific resource (an owned historical ROOT claim), which is distinguishable from sibling signing tools like sign_snack. The 'legacy compatibility' framing and the legacy-vs-arena capture distinction sharpen the purpose, though the name 'takeover' versus the description's 'claim signature' leaves a slight naming/scope mismatch.

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?

The description implies usage ('legacy compatibility') and gives a when-not-to-use hint — new arena capture IDs are not legacy claim IDs — but never names the alternative tool or states prerequisites (e.g. needing a key from confirm_agent_signing_key). The alternative is left to inference rather than routed explicitly.

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