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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so safety needs little elaboration. The description does add two things annotations cannot: the result ordering (newest first) and the quota note 'Never counts toward the daily limit', which is genuinely useful context. It stops there — nothing about what an entry contains or how alert vs briefing emails are distinguished — so with annotations carrying most of the load this sits at a solid 3.

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?

Two tight sentences: the resource and ordering come first, then concrete query triggers. No filler, no restatement of the title.

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 values need not be explained, and annotations cover the safety profile; the description supplies scope, ordering, plan gating, and quota behavior. The only gap is that it doesn't say how mixed alert vs daily-briefing emails are presented, which matters slightly for interpreting results.

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% and the single 'limit' parameter is already documented with its 1–50 range and default in the schema. The description adds nothing about the limit (e.g., what happens when more exist than requested), 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?

Names a specific resource — the alert and daily-briefing emails CapitalSnitch sent the user — with ordering ('newest first'), making it clearly an inbox-style read rather than a content lookup. It does not explicitly name the closest sibling (get_daily_brief) to disambiguate 'briefing email' from 'brief content', so it stops just short of a 5.

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?

Two concrete trigger phrasings ('what alerts did I get today?', 'did anything trigger on my watchlist?') give an agent clear use context. No when-not-to-use or explicit alternative is stated, so the routing burden for adjacent tools like get_daily_brief is left implicit.

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