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

Annotations already cover read-only/idempotent semantics, and the description adds substantial context beyond them: cost ('Free; no user data or credits'), the KEV-absence caveat, the rule that retained withdrawn/excluded evidence is provenance and not active analytics, a prompt-injection warning about untrusted source text, and sequential-call plus HTTP 429/Retry-After handling on the public endpoint.

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?

Purpose and input sourcing are front-loaded, and most sentences carry distinct operational value (cost, provenance, pagination, rate limits). It is longer than average and the safety/rate-limit guidance could be tightened, but no sentence is pure filler.

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 read-only tool with no output schema, the description still tells the agent what comes back (record, retained evidence, revisions, KEV join) and warns about interpretation pitfalls in the returned evidence. Combined with the rate-limit and untrusted-content guidance, nothing an agent needs to call and interpret this tool 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 all three parameters are already documented, including the id forms and the meaning of revisionPage and observationPage. The description adds only a light nudge ('Follow evidence pagination when needed') that maps loosely to observationPage but says nothing extra about the two page parameters or their limits, so the baseline of 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: 'Read one Midkernel Threat Intel record, retained evidence and revisions, plus KEV evidence joined via CVE.' It also names the accepted identifier forms, which lets an agent separate this fetch-by-id tool from sibling listing tools like ti_latest without opening the 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?

'Use a record id from ti_latest, a CVE, or a GHSA id' gives an explicit source for the input and implicitly routes discovery to ti_latest. It does not explicitly exclude any sibling (e.g., ti_daily_report or ti_trends) or state when this tool should not be used, so it stops short of full when/when-not guidance.

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