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

Annotations only declare readOnlyHint; the description goes well beyond by disclosing the return payload (stored publishable token plus DERIVED effective_status/is_valid) and the derivation rule — validity is bounded by the underlying control proof (revoked/suspended/expired domain proof invalidates it) and by its own expires_at, whichever comes first. That is real behavioral context an agent cannot get from structured fields.

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?

Front-loads what the tool does and what it returns, then a clearly separated ACCESS block. Information-dense but every sentence carries weight; the validity explanation is slightly verbose but justified given no output schema.

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?

With no output schema, the description supplies the return shape and the semantics of the derived status fields, and it supplies auth prerequisites. An agent has everything needed to call it correctly and interpret the result.

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 single id parameter is fully documented, so the schema does the heavy lifting. The description restates both accepted formats (Mongo id, ph_dlg_* handle) but adds no syntax detail beyond the schema pattern, 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?

States a specific verb (Get) and resource (one delegation) plus the accepted identifier formats (Mongo id or ph_dlg_* handle). The singular 'one of your delegations' separates it from list_delegations and verify_delegations without needing their schemas.

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 access prerequisites: needs a Proof account, how to authenticate (Claude Code /mcp → Authenticate), and an explicit warning that start_login does not unlock this tool. It does not state when to prefer this over list_delegations or verify_delegation, so it falls short of the 5 bar.

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