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

Annotations only carry destructiveHint=false, so the description does the heavy lifting: it discloses the auth/permission gate, the partial-update semantics ('仅给定键，null清空'), the mandatory read-then-write workflow, and a content-authoring constraint about who may appear in the sign-off. These are behavioral traits not recoverable from the single annotation.

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?

Permission tag is front-loaded, then semantics, then workflow, then authoring constraints — good ordering with no filler. The telegraphic, punctuation-heavy Chinese packs a lot into one block, which slightly taxes parsing but wastes no words.

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 4-parameter nested-object mutation with no output schema, the description covers permissions, update semantics, key vocabulary, style enum behavior, workflow position, and content-authoring policy. Nothing an agent needs to call it correctly is missing.

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%, but the content parameter is an untyped additionalProperties object whose keys the schema cannot document; the description enumerates them (salutations, agenda, hosts, contacts-without-email, closing), which is genuine added meaning. It stops short of explaining value formats or whether unlisted keys are preserved or dropped, so not a 5.

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: 改邀请函content (modify invitation-letter content), and immediately scopes it to 'only the keys given, null clears'. It also names its two workflow siblings (get_activity_letter, render_activity_letter), so an agent can place it precisely in the chain without opening a 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 an explicit ordering: get_activity_letter to obtain version → this tool → render_activity_letter, plus the gate '【需要登录·主办方】' (login + organizer required). It also states content rules (only user facts; signature line only the organizer themselves/organization, third parties go under hosts), which is exactly the when/when-not guidance an agent needs.

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