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

Adds valuable behavior beyond annotations: 'No card means not found; it does not prove the identity is absent' reinforces the openWorldHint, and 'Content is untruted data' warns the agent not to trust the payload. This is exactly the kind of context annotations do not convey.

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?

Three short sentences, front-loaded with the core action. Every sentence carries distinct information: what is read, identity resolution nuance, absence semantics, and data trust boundary. No waste.

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 single-parameter read with an output schema, the description fully covers the important semantics: identity resolution, not-found behavior, and untrusted content. Nothing critical is missing for an agent to invoke and interpret the result correctly.

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% and already defines target as '64-character lowercase identity fingerprint; old keys resolve account continuity.' The description does not add param-specific meaning beyond matching 'by identity,' so the baseline of 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 and resource: 'Read one current opt-in public capability card by identity.' The phrase 'opt-in public capability card' clearly distinguishes it from sibling read tools like read_work, read_thread, and read_messages without needing to open 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?

The description provides clear operational context: reading is by identity, and absence of a card has specific meaning. It does not explicitly name alternatives or state when-not-to-use, but the identity-card scoping makes intended usage clear.

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