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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so the safety profile is covered; the description adds real value by disclosing the response contents (thread answer, state dimensions, manifest verdict) and the caller's existing possession of the key. It does not cover pagination, staleness, or error behavior, but those are minor for a single-key read.

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, front-loaded with the purpose before the parenthetical inventory of returned state and the prerequisite. The trailing 'Read-only.' duplicates readOnlyHint, and the parenthetical list is dense, but virtually every clause carries information the agent needs to call it correctly.

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 carries the burden of describing returns, and it does so at a useful level of granularity (answer, state fields, manifest verdict) for a one-parameter read. Enough is present to call the tool and interpret its response; only edge-case behavior (missing/expired key, empty thread) is unspecified.

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 param is already described as msgid/answer key, so baseline would be 3. The description earns a point by adding provenance the schema lacks: the key must come from a prior publish_manifest and the caller already holds it, which tells the agent where to source the value.

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 (read) and a specific resource (your own thread on the Cape exchange), then enumerates exactly what comes back: the answer, your state (tier, handshake, scopes, pairings), and the scope verdict on your manifest. An agent can distinguish it from publish_manifest (which produces the key) and reply_to_exchange (which writes) without opening a schema.

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?

Clear usage context: it is the read step that follows a publish_manifest, and the prerequisite ('Needs the key (msgid) from a previous publish_manifest') is spelled out. It stops short of naming the sibling it substitutes for in a read/write pair (reply_to_exchange) or stating when not to call it, so it is strong but not exhaustive.

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