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

Annotations already cover safety (readOnlyHint, destructiveHint=false, openWorldHint), and the description adds genuinely non-derivable behavior: API key and credits are required over MCP, pricing is Exa's pass-through with no markup read from its own payment challenge at execution time, and the quote is not a guaranteed fixed price. That cost/auth disclosure is exactly the kind of context annotations cannot carry.

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-loads what it does and when to use it, then the return shape, then the operational caveats. The pricing sentence is long but carries load-bearing pricing/auth information; nothing is padding, though it could be split for scanability.

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?

With no output schema, the description supplies the return fields (title, url, snippet) itself, plus the auth/credits requirement and the non-fixed pricing caveat a caller needs before invoking. Nothing material is left for the agent to guess.

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%, so the schema already documents query, limit, since, domains, excludeDomains and snippets with their bounds. The description only re-states that a snippet accompanies each result, adding no syntax or filter semantics beyond the structured fields. 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 (search) and resource (the web via Exa's index) and explicitly contrasts the interaction model with a sibling: 'a query instead of a url, for when you do not know where to look.' It also names the return shape (title, url, snippet), so an agent can separate it from web_scrape and web_map without opening any 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 a clear selection condition ('when you do not know where to look') and routes the agent onward: 'To read the pages, pass the urls to web_scrape_batch.' It does not state when NOT to use it (e.g. when the url is already known, or vs. web_map/web_crawl), so it stops short of an explicit alternatives matrix.

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