MP4.now MCP Server

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

Beyond the annotations (which flag non-read-only, open-world, non-idempotent), the description adds meaningful behavioral context: it performs a remote download, rejects private-network URLs, and rejects embedded credentials in URLs. Those are security/side-effect details an agent cannot get from the structured fields. It stops short of describing rate limits, failure modes, or what happens to the fetched media afterward.

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 operational flow first, the URL restrictions second. No filler. The slightly muddled 'MP4 or supported media URL' phrasing costs a point but the structure is well front-loaded.

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 safety profile is carried by annotations. Still, for a 9-parameter conversion tool with zero schema descriptions, the omission of the sizing, quality, and metadata-stripping parameters leaves real gaps for an agent trying to configure a conversion correctly.

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 0% across 9 parameters, so the description must carry the load. It explains only source_url (public accessibility, no credentials, no private networks), converter (slug), and wait_for_completion (optional). Six parameters — width, height, quality, strip_metadata, timeout_seconds, background_color — get no mention at all, leaving their purpose and interaction (e.g., how width/height/background_color relate to resizing vs. video) undocumented.

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?

The description names a concrete verb chain (download a media URL, submit to MP4.now with a converter slug) and the resource being converted, which is more than the tool name alone conveys. It implicitly separates itself from get_conversion_status by offering an inline wait option. However, the name says 'image' while the title and description say 'MP4 video', which creates ambiguity about what media types are actually accepted.

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?

"Optionally wait for the result" implies the alternative path (fire-and-poll via get_conversion_status), and "using a converter slug" hints that list_converters is a prerequisite, but neither sibling is named. An agent must infer both the slug-discovery step and the polling fallback rather than being told explicitly.

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 cover the safety profile (readOnlyHint, openWorldHint), and the description adds the key behavioral fact that results are scoped to the caller — identity comes from auth, not arguments. It also names the three data classes returned, which helps the agent know a single call answers both quota and throttling questions.

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?

One sentence, front-loaded with the verb, and every element (credits, usage, rate limit) carries information. Nothing is redundant with the annotations or schema.

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 zero-parameter read tool with an output schema and read-only annotations, the description supplies what's needed: what it returns and that scope is caller-derived. Only minor gaps remain, such as whether values are live or cached and how rate-limit data is represented.

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?

The tool takes zero parameters, so the baseline is 4. The description's use of 'the caller's' correctly signals that scoping is implicit rather than argument-driven.

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 ('Return the caller's MP4.now API credits, usage, and rate limit'), which clearly separates it from the conversion-oriented siblings. It could not be confused with convert_image_url or list_converters, though it doesn't name them explicitly.

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?

Usage is implied rather than stated: an agent can infer this is the tool to call when it needs credit balance or rate-limit state before issuing conversions. There are no explicit when-to-use/when-not conditions or references to alternatives.

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 readOnlyHint=true and openWorldHint=true, so safety is covered. The description usefully adds that a completed job returns an absolute, temporary download URL (signaling expiry), but says nothing about intermediate states, failure states, or whether polling too early errors.

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 short sentences, front-loaded with the action and followed by the one output fact that matters (temporary URL). No 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?

An output schema exists, so return values need not be explained. However, for a polling tool the description omits how to obtain job_id and what state transitions to expect, which are the two things an agent needs beyond the schema.

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 0% and the description says nothing about job_id — not its format, not where it comes from (presumably the conversion call), not whether it is validated. With one undocumented required parameter, the description fails to compensate for the coverage gap.

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 ('Check') and resource ('a MP4.now conversion job'), which is clearly distinct from convert_image_url, list_converters and get_api_usage. It does not explicitly name the sibling it is not, but the job-status intent is unambiguous.

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?

Usage is only implied: an agent infers it should poll this after starting a conversion. There is no statement about when the job must be queried, whether repeated polling is expected, or what to do once the URL is obtained versus calling something else.

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 readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds that the catalog is 'live' and that returned slugs are 'valid', which is modestly useful, but it says nothing about whether results are paginated/truncated, how large the catalog is, or how search matching works. 'Live' also sits slightly at odds with openWorldHint=false, though this is interpretive rather than a contradiction.

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?

A single front-loaded sentence with no filler; the verb, resource, and illustrative output examples are all in the first clause chain. Nothing is redundant or padded.

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 tool is a simple two-parameter read. Still, for a discovery tool the agent needs to know how 'search' filters and whether 'limit' implies truncation of a larger catalog; those gaps keep it at minimum viable.

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 0% and both parameters (limit, search) carry only titles and defaults in the schema. The description uses the word 'Search' but never explains matching semantics (slug substring, name, case sensitivity) or what 'limit' truncates against. With low coverage the description should compensate, and it does not.

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 ('Search') against a named resource ('the live MP4.now converter catalog') and clarifies the return type with concrete examples of valid slugs (mp4-to-mp3, mov-to-mp4). An agent can immediately tell this is a discovery/lookup tool, distinct from the conversion-execution siblings convert_image_url and get_conversion_status.

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 purpose implies usage (find a valid converter slug before invoking a conversion), but there is no explicit when-to-use or when-not statement, nor any reference to the sibling tools or to prerequisites. The agent must infer that this is the entry point for the workflow.

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