mutualAuthDeriveSession

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

With no annotations provided, the description carries the full burden of behavioral disclosure. It explains the deterministic nature, the canonical JCS + sha256 computation, the required inputs, and the return value or failure reason. It does not explicitly state whether the operation has side effects, but the 'derive' and 'compute' language strongly implies a pure, stateless operation.

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 deliver a high density of relevant information without waste. The most important facts (what it does, determinism, algorithm, return value) are all present, and the description is front-loaded with the core purpose.

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 does a good job of explaining the return value and failure behavior. It could be more explicit about the policy parameter's role and any preconditions (e.g., that both attests must be generated by mutualAuthBuildCertificate), but overall it is adequate for correct invocation.

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?

The schema's parameter descriptions are minimal type names (e.g., 'MutualAuthPolicy', 'MutualAuthAttest'), but the description adds meaning by explaining that agent_attest and is_attest are the two sides' Attests and that the derivation uses canonical JCS + sha256 of chosen_version, cert ids, and nonces. This helps the agent understand what values to provide even though the schema is sparse.

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?

The description states a specific verb ('Derive') and resource ('shared mutual-auth session record'), and clearly distinguishes this from sibling tools like mutualAuthBuildCertificate and mutualAuthVerifyAttest by focusing on deriving a session from both sides' Attests. It also names the key output (session_id + certificates + expiry bounds), making the purpose unambiguous.

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 clearly conveys the context: it creates a shared session from both sides' attests and emphasizes both parties must compute identical session_id. It does not explicitly name alternatives or exclusion criteria, but the context is sufficient to guide an agent when this tool is appropriate versus other mutual-auth operations.

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