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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false. The description adds real operational context beyond that: statelessness, 32 KB payload cap, 60 RPM rate limit, demo/L402 payment of 15 sats, and a 400 on invalid input. That said, it never describes what the response shape or error payloads look like beyond the status code, so it sits at a solid but not maximal level.

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 sentences, front-loaded with the purpose before the exclusion and the operational parenthetical. Slightly dense with pricing/rate-limit details packed into one clause, but no sentence is wasted.

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 an output schema present, return values need no explanation. The description covers cost model, rate limit, size cap, default algorithm, error status, and the alternative tool — everything an agent needs to invoke it 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?

Schema coverage is 100%, so the baseline is 3. The description still adds value by disclosing that clustering_method defaults to 'tf_idf_semantic_graph' and that the input is subject to a 32 KB limit, neither of which is in the schema. These are small but genuine clarifications beyond the structured data.

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+resource: 'Discovers latent thematic clusters, subtopic branches, and conceptual relationships across document corpora.' It also names the sibling it is not for (summarize_temporal_timeline), so an agent can separate clustering from chronology without opening schemas.

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 explicit use cases ('structuring broad search results into distinct thematic silos or generating table of contents taxonomies') and an explicit exclusion routing to summarize_temporal_timeline for chronological milestones. Nothing is left to inference about when to pick this tool.

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