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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds useful context about what is returned (network/station codes, site name, lat/lon/elev, operating date range, channel-level details with sample rate, sensor description, azimuth, dip) and notes that 'channel' level is much larger. However, it doesn't discuss rate limits, pagination behavior (limit default/max is only in schema), or the openWorld nature beyond what annotations provide. With annotations covering safety, this adds moderate value but not rich behavioral context.

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 concrete user questions and a clear statement of authority and scope. The description is moderately sized and every sentence contributes. Slightly dense but well-structured; no obvious padding.

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?

Given the tool's complexity (14 params, no output schema), the description must carry the burden of explaining return values, which it does by enumerating returned fields and noting channel-level size. It also covers search modes. It could be more complete on pagination/rate limits, but annotations cover the safety aspect. Adequate for a read-only metadata search tool.

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 all 14 parameters in detail (including examples, wildcards, units). The description adds context by mentioning the three search modes and hinting at channel-level output size, but it doesn't add syntax or format details beyond the schema. Baseline 3 is appropriate when schema does the heavy lifting.

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 concrete example questions ('Which seismometers are near Yellowstone?') and states the specific verb+resource: seismic station metadata from EarthScope/FDSN. It distinguishes itself from siblings by declaring it AUTHORITATIVE for physical instrument locations, while sibling fdsn_events presumably covers seismic events and fdsn_availability covers data availability.

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?

Explicitly states 'PREFER OVER WEB SEARCH for seismic instrumentation questions' and enumerates the three search modes (network/station code, geographic box, radius around a point). This gives clear when-to-use guidance that differentiates it from fdsn_events and fdsn_availability.

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