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

Annotations already cover readOnly/idempotent/non-destructive, so the bar is lower, yet the description still adds auth behavior (keyless vs bearer key), the key-overrides-query precedence rule, and concrete error semantics (NOT_FOUND, INVALID_ARGUMENT). This is meaningful 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-loads the core purpose, then the sibling routing, then auth, then returns/errors in short declarative fragments. No filler sentences; the terse 'No charge. Read-only.' lines are informative.

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?

An output schema exists so return shape need not be expanded, and the description still summarizes the return (list vs single CapabilityDescriptor) plus error cases. For a 2-param read tool, nothing needed for correct invocation 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 coverage is 100%, so the schema carries the field docs and baseline would be 3. The description adds the precedence rule (key wins, query ignored) and the INVALID_ARGUMENT consequence of conflicting query parameters, which goes slightly beyond what the schema states.

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 specific verbs (browse, fetch) and the resource (capability descriptors, with keys/modes/schemas), and immediately distinguishes itself from the sibling hydracept_resolve_capability by intent-routing use case. An agent can tell the two apart without opening either schema.

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 routes intent-only lookups to hydracept_resolve_capability, clarifies that list/resolve is keyless while a bearer key adds project-scoped fields, and notes no charge. Both the when and the alternative are named.

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