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

Annotations already declare readOnlyHint=true, openWorldHint=true, idempotentHint=true, and destructiveHint=false. The description adds useful context beyond these: 'No auth, US Gov public domain' clarifies access requirements, and 'active' stations signals the data is a live snapshot. It does not mention rate limits or pagination, but those are less critical for a read-only list tool.

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?

Four sentences with no filler: purpose, scope, filtering, return fields, downstream usage, and source/auth are each addressed once. Information is front-loaded with the core action first, and every clause earns its place.

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 simple list tool with three optional parameters, the description covers the essential context: what it returns, the geographic scope, how to filter, how to chain with sibling tools, the data source, and authentication. An output schema exists, so the lack of detailed return-value documentation is acceptable. Nothing an agent needs to decide whether and how to call it is missing.

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 baseline is 3. The description adds minimal semantic value by giving concrete state examples ('CA, FL, NY') and implying a filter behavior, but it does not elaborate on limit or tidal_only beyond what the schema already states. It neither hurts nor significantly helps parameter comprehension.

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 a specific verb and resource: 'List active NOAA CO-OPS tide gauge stations with their IDs, names, coordinates, and metadata.' It further distinguishes itself from sibling tools (coops.tides.predictions, coops.tides.water_level, coops.tides.conditions) by clarifying that it returns station identifiers for downstream use. The scope ('Over 300 stations covering US coastal states...') adds concrete specificity.

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 clearly frames this tool as the entry point for station discovery and explicitly tells the agent to 'Use the returned station_id values with coops.tides.predictions, coops.tides.water_level, and coops.tides.conditions.' It provides filtering guidance ('Filter by state abbreviation...') but does not explicitly state when not to use this tool versus a sibling, so it stops short of a 5.

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