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

With no annotations, the description carries the full burden. It discloses the return format (clean markdown with title, author, published date, domain trust tier) and the paywall-handling behavior. However, it omits the truncation behavior implied by max_chars (e.g., body truncated to max_chars) and potential failure modes for unreachable pages. Still well above minimum viability.

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?

The description is compact and front-loaded: it opens with the core purpose, then covers usage limits, output, and the critical distinction from the search tool. Every sentence adds value, with no redundancy or fluff.

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 simple URL-fetch tool, the description covers purpose, usage, output format, paywall handling, and the relationship to the search sibling. The primary gap is the undocumented max_chars parameter and its truncation behavior, which would make the description nearly complete.

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 0%, so the description must compensate. While 'url' is contextually explained ('the URL for'), the 'max_chars' parameter is not mentioned at all. The agent is left to guess the parameter's effect (likely output truncation), which is a significant gap given the schema provides no description.

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 clearly states 'Read ONE specific page you already have the URL for' — a specific verb ('Read') plus a specific resource ('ONE specific page'), with the key constraint that the URL must already be known. It explicitly distinguishes itself from search tools by naming tengu_v3_research_web_search, and the output characteristics (markdown, metadata, trust tier) further clarify its role.

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?

The description gives explicit usage timing: 'call ONLY after a search returned the link, never to discover pages.' It also provides a quantitative guideline ('at most the 2-3 most load-bearing links per question') and names the alternative tool for discovery. This is exemplary guidance.

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