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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is fully covered by structured data. The description adds no behavioral context of its own - nothing about result shape, matching/narrowing behavior, or whether a non-matching keyword yields empty or fallback content.

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 sentences with no filler, and the core purpose is front-loaded. It is efficient, though the second sentence is a fragment that could carry a bit more useful detail without bloat.

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 trivial one-optional-param read tool with full annotations this is close to adequate, but with no output schema the description should at least hint at what comes back (list of Q&A entries, single answer, etc.). That gap is minor but real.

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?

With a single optional parameter and 100% schema description coverage (including examples like 'delivery', 'format', 'pay' in the schema itself), the schema carries the burden. The description's 'optional keyword filter' merely restates that the parameter exists and is optional.

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+resource: it answers common questions about the ISBN service. An agent can immediately tell this is a documentation/FAQ lookup, distinct from the sibling offer/link/info tools, though it never explicitly contrasts itself with them.

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?

'Optional keyword filter' implies you may call it with or without a query, but there is no explicit when-to-use guidance, no mention of what to do when no keyword matches, and no routing against sibling tools. Usage is only implied.

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