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, and it does so thoroughly. It explains the encoding algorithm, SET OF sorting behavior, indefinite-length construction with 0x80 + EOC, constraints on OID arcs and time formats, the raw escape hatch, and the mutually exclusive modes. It also lists output fields such as der_conformant, structure_tree, truncated, and warnings, giving the agent a clear picture of what will happen.

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?

The description is long but well organized into labeled sections: algorithm, parameters, output, and notes. The core purpose is front-loaded, and each section earns its place given the complexity of the tool. Minor redundancy with the input schema description prevents a 5, but the structure is appropriate for the subject matter.

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 tool with no output schema and no annotations, the description covers the critical calling context: input DSL forms, encoding modes, mutual exclusion, constraints, and output field names. It stops short of fully defining the semantics of every output field or error behavior, but it is complete enough for an agent to invoke the tool correctly and interpret the main results.

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 input schema already provides 100% parameter coverage with detailed descriptions, so the baseline is 3. The description adds value beyond the schema by giving concrete DSL examples, explaining explicit vs implicit constructed forms, clarifying the meaning of both-false mode, and specifying constraints like OID arc limits and unused_bits range. This goes beyond the schema's own documentation.

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 opens with a specific verb and resource: '把 JSON 节点 DSL 编码为 DER 字节（X.690）'. It immediately distinguishes DER encoding from decoding or other encodings and further clarifies the two BER/DER modes. The purpose is unmistakable even without opening the 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?

The description clearly explains when to use DER mode, BER indefinite mode, or the teaching BER mode, and states that der and ber_indefinite are mutually exclusive. However, it never explicitly compares this tool with sibling tools such as cbor_encode or asn1_parse, so guidance for choosing this tool over alternatives is only implied rather than stated.

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