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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), so the description is free to add operational detail instead. It discloses that no API key is required ('free, no key'), the resolution step, the titleSearch servlet, and that each result carries a direct PDF link. It does not mention rate limits or pagination, which keeps it from a 5.

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-loaded with the core action and key attributes ('free, no key') before moving to resolution mechanics and sibling routing. Three sentences, all earning their place; the category enumeration is the only part that could be trimmed or moved.

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 6-param read-only search tool with full schema coverage, annotations, and an output schema, the description covers domain, resolution path, output shape ('metadata plus a direct PDF link'), and sibling differentiation. 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%, so the schema already documents all six parameters including defaults and the stockCode format. The description adds category-code meaning ('10000 Announcements, 20000 Circulars, 40000 Financial Statements/ESG…'), which is genuinely useful context beyond the schema's 'e.g. 10000 or 40000'. Baseline 3 is appropriate given the schema does the heavy lifting.

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 gives a specific verb and resource ('List Hong Kong listed-company announcements from HKEXnews'), explains the resolution mechanism (5-digit code or company name to internal stockId, titleSearch servlet), and explicitly distinguishes itself from the sibling sec_edgar_fulltext ('use sec_edgar_fulltext for US filings'). An agent can select it immediately.

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?

It states the intended domain ('HKEX/SEHK primary disclosures') and names the alternative for the adjacent use case (US filings), providing explicit when-to-use and when-to-use-something-else guidance. The category code list also tells the agent which categories exist for filtering.

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