parse_envelope

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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, but the description adds genuinely new behavior: it fails closed on layout rules and never normalises malformed input into a partial result. It also covers the auth aspect (no key required), which annotations do not.

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 dense sentences, front-loaded with the operation and scope, with no filler. The reference to 'companion draft sec. 2/sec. 4' is slightly opaque jargon, but each clause carries information.

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 an output schema present, return values need not be described; the description instead covers input format, key requirement, and failure semantics. Only explicit sibling routing is missing for a tool with three neighbors.

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 0% and the schema only labels the field 'Envelope Hex', so the description carries the burden — and it does, specifying the input is a single 128-byte hex envelope. It does not clarify casing, prefix, or exact byte-length validation behavior.

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+resource ('Structural decode of one AE-128 attestation envelope') with a concrete size/format qualifier (128 bytes, hex). The 'No organ key needed' clause implicitly distinguishes it from the sibling verify_envelope, though no sibling is named explicitly.

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?

There is no explicit when-to-use/when-not statement or named alternative. The keyless framing ('No organ key needed') implies this is the structural-only counterpart to verify_envelope, but the agent must infer that routing rather than being told.

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