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

Annotations already declare readOnlyHint, destructiveHint=false and openWorldHint=false, but the description adds genuinely new behavior: the text is kept verbatim, the interaction is anonymous and nothing is saved. It could go further on length limits or what the reader returns, but the privacy and fidelity guarantees are the substantive additions.

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?

Four short sentences, front-loaded with the core action and its interaction model, then the privacy guarantee, then routing and exclusions. No sentence is redundant against the others.

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?

An output schema exists, so return values need not be explained, and the tool is simple with two parameters, one required. The description covers purpose, interaction, privacy, routing and exclusions; only the optional 'title' parameter's effect on the viewer is left unaddressed.

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 50%: the required 'text' parameter is fully documented in the schema, including the verbatim/no-rewrite rule that the description also echoes. The optional 'title' parameter is undocumented in both places, and the description adds no syntax or formatting guidance beyond the schema, so the baseline 3 applies.

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 plus resource: 'Open an interactive reader for a Mandarin article excerpt, message or subtitle passage.' It also names the sibling it is not for ('Use inspect_mandarin_word for one specific word'), so an agent can discriminate it from siblings without opening any 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?

Gives the triggering condition (a passage 'the user supplies'), the alternative for a different need (single-word lookup via inspect_mandarin_word) and explicit exclusions ('Does not fetch links or transcribe media'). Use and non-use cases are both spelled out.

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