tnd_start_chapter_download

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

With no annotations, the description carries the full behavioral burden. It implicitly discloses asynchronous behavior ('启动...任务', then '完成后'), which is genuinely useful, but says nothing about what the call returns (job id?), how to track progress (tnd_get_status / tnd_wait_job), behavior when the chapter is already downloaded, or whether it overwrites files.

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?

Two short clauses with no filler, and the core action is front-loaded before the follow-up instruction. Nothing is wasted, though the redundancy with the schema's index description is minor slack.

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 2-parameter tool with full schema coverage and no output schema, the description covers purpose and the next step. It remains incomplete on the async contract (what is returned, how completion is detected) and on sibling selection among the four start_* tools, which is the main ambiguity an agent faces here.

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 description coverage is 100% and both parameters (book_id, index) are documented in the schema. The description restates 'index 是 1-based 章节序号', which duplicates the schema's '章节序号，从 1 开始' and adds no new meaning, 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 and resource: '启动单章下载任务' (start a single-chapter download task). The qualifier '单章' (single chapter) implicitly separates it from the bulk siblings tnd_start_book_download and tnd_start_discrete_downloads, though those siblings are never named.

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 a clear follow-up step ('完成后用 tnd_read_downloaded_chapter 读取'), which tells the agent what to do after starting. However, it never states when to pick this over tnd_start_download, tnd_start_book_download, or tnd_start_discrete_downloads, nor any preconditions such as whether the chapter must be checked first with tnd_check_chapters.

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