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

Annotations already declare readOnlyHint, so the bar is lower, and the description still adds genuine behavioral context: it discloses the decryption result per channel type and that unreadable envelopes surface as <ciphertext>. It stops short of saying how many messages come back or how the cursor terminates.

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?

Front-loads the operation, ordering, and required parameter before the encryption detail, which is the right priority. The encryption clause is dense and slightly convoluted in its middle clauses but every sentence carries information an agent needs.

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?

Covers purpose, required input, pagination, and the non-obvious encryption outcome for a read-only tool whose safety profile is already in annotations. With no output schema, however, it never describes the shape of a returned message or the pagination envelope, leaving the agent to discover that at call time.

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 75%, so the schema largely documents channel_id, cursor, and space_id, and the description only restates the auto-resolution of space_id. The limit parameter (default 50, max 200) is never mentioned, so the description adds little beyond the schema.

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?

Names a specific verb and resource ('List recent text messages in a persistent channel') plus ordering and pagination model, which tells an agent exactly what it gets. It does not, however, distinguish itself from near-siblings like mIRC_history_edge or mIRC_get, so the reader must infer the boundary.

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?

Gives the required calling convention ('Pass channel_id; the backing space is resolved automatically') and notes open vs group-key channels, which helps the agent decide relevance. There is no explicit when-to-use/when-not guidance relative to mIRC_history_edge, mIRC_list, or mIRC_get, so routing remains implied.

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