Calmido Phone Number Lookup

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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuine value by previewing the returned payload (community verdict, report counts, business registration, evidence link), which tells the agent what it will learn without opening the output schema. It stops short of stating behavior for a missing or unknown number.

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 sentences, front-loaded with the action and the payoff, no filler. Minor redundancy: the second sentence about the id restates the schema's parameter description almost word for word, so it earns only partial credit.

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?

With an output schema present, the description needn't detail return values, and it still usefully summarizes them; annotations carry the safety profile. The one gap left for an agent is edge-case behavior (unknown number, missing entry), which neither description nor annotations address.

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 `id` parameter is documented in-schema with the same E.164-digits phrasing. The description essentially repeats that constraint verbatim rather than adding new meaning (no format examples, no note on what an invalid id yields). Baseline 3 for a schema-covered parameter.

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 ('Retrieve') and resource ('who is behind a phone number from the Calmido directory'), then enumerates exactly what comes back: verdict, report count, top category, registered business, evidence link. An agent can distinguish this from the sibling `search` because the description frames this as the follow-up lookup for a known id.

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 clause 'The id is the one `search` returned' establishes the intended usage sequence: search first, then fetch. What's missing is any routing against the other sibling, `lookup_phone_number`, which is presumably a competing way to resolve a number — the agent gets no signal on when to pick this over that.

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

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

Annotations already declare readOnly/idempotent/non-destructive, and the description adds genuinely new operational context: rate limiting per address, an error that reports seconds to wait, an error on invalid numbers, and precise semantics for each verdict including the important caveat that 'empty' is not a sign the number is safe. The distinction between 'restricted' (identity erased, reports remain) and 'unavailable' (lookup unreadable, says nothing) is exactly the kind of nuance 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 purpose, then usage, then formats, then the verdict taxonomy, then error/rate-limit behavior — a sensible ordering with no filler sentences. It runs long mainly because the seven-way verdict enumeration is spelled out, which is defensible but costs some density.

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 the description still covers the failure modes (invalid number, rate limit, unreadable lookup) and the interpretive pitfalls of the verdict values. An agent has everything needed to decide to call it and to judge the result.

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 baseline is 3, but the description adds practical meaning: it restates accepted international and national formats with examples and notes that `country` is only needed for a national number outside the Netherlands. The per-verdict enumeration also ties output meaning back to the lookup rather than to any single parameter, so this is modestly above baseline.

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 ('Look up who is behind a phone number') plus the geographic scope (NL/BE/LU) and exactly what data comes back (community reports, spam/scam categories, trust verdict, registered business). The named data source ('Calmido phone directory') further pins it down, so an agent can distinguish it from the generic `fetch` and `search` siblings at a glance.

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 concrete triggering conditions: 'Use it whenever someone asks who called them, whether a number is safe, spam or a scam, or which company a number belongs to.' That is strong positive routing guidance, but there is no when-not clause and no explicit mention of the `search`/`fetch` siblings as alternatives, 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.

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

Annotations already cover read-only, idempotent, non-destructive, closed-world behavior, so the bar is lower. The description adds real value beyond them: it discloses that a match may not exist ('if any') and describes the two-step workflow into `fetch` for verdicts and reports, which annotations cannot express.

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?

Three short sentences, front-loaded with the resource and scope, then input format, then return and next step. No sentence is redundant with another or with structured fields.

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 single-parameter read tool with an output schema and full annotation coverage, this covers everything the agent needs: scope, accepted format, negative constraint, possibility of no match, and where to go next. Nothing essential 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 baseline is 3. The description goes beyond the schema by constraining the input negatively ('not a name or free text') and giving both international and national formats, which reduces wasted calls with names as queries.

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 ('Find a phone number in the Calmido directory') plus the geographic scope (NL/BE/LU), and the final sentence distinguishes it from `fetch` by explaining the handoff. It does not differentiate itself from the sibling `lookup_phone_number`, whose name suggests an overlapping purpose, leaving some ambiguity for the agent.

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 says what the query is and is not ('it is not a name or free text') and describes the follow-on step ('Pass its id to `fetch`'), which gives clear usage context. There is no explicit rule for choosing this over `lookup_phone_number`, so the alternative-selection guidance is incomplete.

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