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

Annotations cover the safety profile (readOnly, idempotent, non-destructive), and the description layers on substantial extra behavior: typical latency (1-5s), gzipped payload, a USD 2 price with no free tier, a per-IP daily cap, and an explicit prompt-injection warning about untrusted endpoint data. That is genuinely valuable operational context beyond the structured fields.

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-loaded with purpose, latency, and price, then the data-provenance caveat. Dense but each clause carries information; the security warning is slightly verbose but justified. No wasted filler.

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 carries the return explanation ('Returns every current-snapshot record', gzipped) along with cost, latency, and rate-cap context. Complete enough to call it correctly, though the exact record shape is left unstated.

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?

Only one optional parameter, and the schema already documents it fully (100% coverage, 'Filter: exact source id'). The description restates that source restricts to one source, adding no syntax or format detail beyond the schema. Baseline 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?

States a specific verb (download) and resource (full current-snapshot index, gzipped), and the 'full current snapshot' framing distinguishes it from the query-style siblings. However, it never names the sibling alternatives (query_agent_index, export_agent_index), so the agent must infer which one to pick.

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 implies usage (get the whole snapshot, optionally restricted by source) but gives no explicit when-to-use/when-not, no prerequisite conditions, and no routing to the obvious siblings query_agent_index or export_agent_index. An agent comparing tools gets no guidance on which to choose.

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