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

Annotations only cover the read-only/idempotent safety profile; the description goes well beyond them by disclosing the returned fields, DST-edge-case behavior (nonexistent and ambiguous wall times flagged), offline tz-database execution, cost ($0.01 USDC via x402/Solana), and an alternative HTTPS endpoint. That is exactly the kind of context annotations cannot carry.

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 the core purpose and output shape, then inputs, then pricing/transport. It is dense but nearly every clause is functional; the payment and endpoint sentences are slightly tacked-on but relevant to invocation.

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?

There is no output schema, yet the description enumerates the returned fields, edge-case flags, and transition metadata, so an agent knows what comes back. For a 3-parameter read tool this fully covers what the agent needs.

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 accepted time formats, the from_zone default of UTC, fixed offsets, and the 10-zone cap. The description restates these rather than adding new syntax or edge-case semantics, so the baseline 3 applies.

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 and resource ('Convert a time between IANA time zones with DST awareness') and immediately scopes the exact output fields (offset, abbreviation, DST flag, next transition). No sibling tool overlaps, and the DST-awareness qualifier distinguishes it from a naive format_convert.

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 clear input-context guidance ('Accepts ISO 8601, HH:MM, epoch seconds/milliseconds or "now"') and a capacity limit ('up to 10 target zones'), which tells an agent when this tool fits. It does not name an alternative or an explicit when-not condition, but no sibling is close enough to require it.

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