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

No annotations are provided, so the description carries the full burden. It discloses the fetching mechanism (concurrent HTTPS), the timeout (5 s each), the parsing approach (lightweight HTML parser), and the exact return format for both success and error cases. This goes far beyond the schema and gives the agent a precise mental model of what happens when the tool is invoked. There is no contradiction with annotations since none exist.

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 three sentences long, each serving a distinct purpose: (1) defining the tool's purpose and components, (2) providing usage scenarios and alternatives, (3) detailing technical behavior and return format. There is no fluff or redundancy; every sentence carries essential information, and the most critical information is front-loaded in the first sentence.

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 tool with one parameter, no annotations, and no output schema, the description is remarkably complete. It covers the inputs (domain), the behavior (concurrent fetches, timeout, parsing), and the output structure (composite CheckResult with status, meta, robots, sitemapPresent). It also implicitly handles edge cases like missing sitemap via 'sitemapPresent'. The description leaves no critical gaps for an agent to reasonably invoke this tool correctly.

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?

The schema already provides a comprehensive description of the 'domain' parameter, including the requirement that it be a public FQDN with IPs, ports, paths, and protocol prefixes rejected (100% schema coverage). The description adds only implicit context about the domain being used as the base for fetching /, /robots.txt, and /sitemap.xml, but does not elaborate on the parameter itself. Given the high schema coverage, the baseline of 3 is appropriate.

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 opens with 'Core dossier check: Snapshot a domain's public web surface', which clearly combines a specific verb ('snapshot') with a specific resource ('domain's public web surface'). It then enumerates the concrete components (robots.txt, sitemap.xml, head metadata), making the scope unambiguous. It also explicitly distinguishes from sibling tools by naming dossier_headers and dossier_redirects for other concerns.

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 scenarios: 'Use for SEO audits, content discovery, or verifying metadata before sharing'. It also provides exclusionary guidance by stating 'for HTTP headers use dossier_headers, for redirect behavior use dossier_redirects', which tells the agent exactly when not to use this tool in favor of alternatives. This is the gold standard for usage guidance.

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