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

With no annotations provided, the description carries the full burden and does so well: it discloses that the operation is public-key encryption by anyone, binds the ciphertext to the identity, enforces a 1-255 byte plaintext limit due to KDF counter constraints, and specifies the output as DER-encoded C1/C3/C2 structure up to 367 bytes. This is rich behavioral context beyond a simple 'encrypt' statement.

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 compact and front-loaded with the key action and access model. However, it begins with a duplicated '[sm9_ibc] [sm9_ibc]' tag that adds noise and no informational value.

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 non-destructive encryption tool with no output schema and no annotations, the description is remarkably complete: it covers all three parameters, their constraints, the output fields, the output encoding, and the output size limit. An agent has enough context to call it correctly without extra lookups.

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%, so the baseline is 3, but the description adds meaningful semantics: master_public_key_in_pem must be the Enc-kind public key, identity is tied to the ciphertext, and plain_data_in_hex has explicit size limits and KDF constraints. This goes beyond the schema descriptions without fully replacing them.

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 clearly identifies the operation as SM9 identity-based encryption ('SM9 标识加密') and states that anyone holding the master public key can encrypt, which distinguishes it from sibling operations like sm9_decryption, sm9_sign, and sm9_verify. It also specifies the required inputs and output format.

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 gives clear usage context: encrypt for a specific identity using the Enc-type master public key. It does not explicitly name alternative tools or provide exclusion criteria, but the identity-based encryption workflow is sufficiently clear for an agent to select it.

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